Cell-Mode MPLS over ATM Overview, Configuration, and Verification
This section introduces you to cell-mode MPLS over ATM configuration. In MPLS over ATM networks, routers are connected to ATM-based provider networks consisting of ATM switches that forward data based on virtual circuits (VCs) provisioned on the ATM switches. Cell-mode MPLS uses the virtual path identifier/virtual channel identifier (VPI/VCI) fields in the ATM header as the label value.
ATM VCs exist locally (on a link between two adjacent ATM switches or two CPEs) and have two identifiers: VPI and VCI. These two identifiers are often referred to as a VPI/VCI pair. VPI and VCI numbers are part of ATM cell headers, and they are, therefore, carried in each ATM cell. Because there are two identifiers, you can have two different types of ATM connections: virtual path and virtual channel. This hierarchy allows aggregation of the number of virtual channels into a single pipe (virtual path) between sites that need a large number of VCs.
The ATM switch is responsible for switching ATM cells on both the VC and VP. When the ATM switch is configured to switch cells on a VC, it has to look at both VPI and VCI fields of the cell in order to make a switching decision. Switching is done based on a table containing (port, VPI, VCI) tuplets for the input and output side of the VC. On Cisco IOS ATM switches, you can see this table with the show atm vc command. You can also configure the ATM switch to switch cells based only on the port and VPI number; this is called VP switching. For VP switching, the ATM switch uses a table consisting of (port, VPI) pairs for input and output. You can see this table on Cisco IOS ATM switches with the show atm vp command. When VP switching, the ATM switch uses only the VPI field of each ATM cell to make a switching decision, which reduces processing time. The same holds true for cell header rewrites. In VC switching, both VPI and VCI fields of the cell header are rewritten and possibly changed. However, in VP switching, only VPI fields can be changed, and the VCI field remains the same end-to-end.
Basic Cell-Mode MPLS Configuration and Verification
Figure 2-7 shows a basic cell-mode MPLS network in which R1 and R2 perform the ATM Edge LSR function while LS1010 ATM switches A1 and A2 serve as the ATM LSR.
Basic Cell-Mode MPLS Configuration Flowchart for Edge LSRs
Figure 2-8 shows the configuration flowchart to set up basic cell-mode configuration on the Edge LSR R1 and R2.
Basic Cell-Mode MPLS Configuration Flowchart for LSRs
Figure 2-9 shows the configuration flowchart for LSR A1 and A2.
Basic Cell-Mode MPLS Configuration Steps
The configurations for basic cell-mode MPLS are based on the configuration flowcharts outlined in Figure 2-8 and Figure 2-9. The functions of the Edge ATM LSRs are performed by routers R1 and R2, and the ATM switches A1 and A2 function as ATM LSRs in the cell-mode MPLS domain.
Configuration Steps for Edge ATM LSR
This section outlines the steps in the configuration of the Edge ATM LSR R1 for ATM or cell-mode MPLS. Ensure that loopback and interface IP addresses are preconfigured before following the steps:
Step 1. | Enable CEF—As shown in Example 2-24, enable CEF globally. Repeat the same steps on R2.
Example 2-24. Enable CEF
R1(config)#ip cef
| Step 2. | Configure the IGP routing protocol—As shown in Example 2-25, configure OSPF as the IGP routing protocol. Repeat the steps on R2.
Example 2-25. Configure IGP for IP Reachability
R1(config)#router ospf 100
R1(config-router)#network 10.10.0.0 0.0.0.255 area 0
| Step 3. | Configure MPLS forwarding on the interface—Create an MPLS subinterface on the ATM link to the connected ATM switch. Enable MPLS forwarding on the ATM subinterface. Example 2-26 demonstrates this step.
Example 2-26. Enable MPLS Forwarding
R1(config)#interface atm2/0.1 mpls
R1(config-subif)#description Connection to A1
R1(config-subif)#ip address 10.10.20.1 255.255.255.252
R1(config-subif)#mpls ip
_____________________________________________________________________
R2(config)#interface atm2/0.1 mpls
R2(config-subif)#description Connection to A2
R2(config-subif)#ip address 10.10.20.10 255.255.255.252
R2(config-subif)#mpls ip
|
Configuration Steps for ATM LSR
This section demonstrates the steps to configure ATM switches A1 and A2. It is assumed that CEF is enabled on the switches and IP addresses are configured on the appropriate interfaces.
Step 1. | Configure OSPF as the IGP routing protocol?a class="docLink" href="#ch02ex27">Example 2-27 summarizes the step to configure OSPF on A1. Repeat the step on A2.
Example 2-27. Configure IGP for IP Connectivity
A1(config)#router ospf 100
A1(config-router)#network 10.10.0.0 0.0.255.255 area 0
| Step 2. | Enable MPLS forwarding on the interface—Enable MPLS forwarding on the ATM physical interfaces, as shown in Example 2-28.
Example 2-28. Enable MPLS Forwarding
A1(config)#interface atm1/0/0
A1(config-if)#mpls ip
A1(config)#interface atm 1/0/1
A1(config-if)#mpls ip
|
Note that no configuration has been made on the MPLS ATM subinterfaces on the Edge ATM LSRs or LSRs with regards to the control-vc using the mpls atm control-vc command. This implies that all the control plane information is propagated and exchanged using the default control VC VPI/VCI values of 0/32. However, the user can change the control-vc associated on an interface in a cell-mode MPLS network. Changes made to the VPI/VCI values associated to the control-vc on an LSR interface must also be made on the connected LSR's interface to enable proper exchange of control plane information.
Verification of Basic Cell-Mode MPLS Configuration
The following steps outline the verification process for cell-mode MPLS operation. All verifications outlined were performed on Edge ATM LSR R1 and ATM LSR A1:
Step 1. | Verify CEF is enabled on the router interfaces on Edge LSR R1, as shown in Example 2-29.
Example 2-29. Verify CEF Is Enabled on the Interfaces
R1#show cef interface atm2/0
ATM2/0 is up (if_number 12)
<truncated>
IP CEF switching enabled
IP Feature Fast switching turbo vector
IP Feature CEF switching turbo vector
| Step 2. | As shown in Example 2-30, verify that MPLS forwarding is enabled on the appropriate interfaces on R1 and A1.
Example 2-30. Verify MPLS Forwarding
R1#show mpls interfaces
Interface IP Tunnel Operational
ATM2/0.1 Yes No Yes (ATM tagging)
_____________________________________________________________________
A1#show mpls interfaces
Interface IP Tunnel Operational
ATM1/0/0 Yes No Yes (ATM tagging)
ATM1/0/1 Yes No Yes (ATM tagging)
| Step 3. | Verify the status of the LDP discovery process by issuing show mpls ldp discovery. This command displays neighbor discovery information for LDP and shows the interfaces over which the LDP discovery process is running. Example 2-31 shows neighbor discovery information and interfaces where LDP is running on R1 and A1. The xmit/recv field indicates that the interface is transmitting and receiving LDP discovery Hello packets.
Example 2-31. Verify MPLS LDP Discovery
R1#show mpls ldp discovery
Local LDP Identifier:
10.10.10.101:0
LDP Discovery Sources:
Interfaces:
ATM2/0.1: xmit/recv
LDP Id: 10.10.20.101:1; IP addr: 10.10.20.2
LDP Id: 10.10.20.102:2; IP addr: 10.10.20.6
_____________________________________________________________________
A1#show mpls ldp discovery
Local LDP Identifier:
10.10.20.101:0
LDP Discovery Sources:
Interfaces:
ATM1/0/0: xmit/recv
LDP Id: 10.10.10.101:1; IP addr: 10.10.20.1
ATM1/0/1: xmit/recv
| Step 4. | Issue show mpls ldp neighbor to verify the status of LDP neighbor sessions. Example 2-32 shows that the LDP session between R1 and A1 is operational. Downstream on demand on R1 indicates the downstream on demand method of label distribution is used for the LDP session between R1 and A1 in which the LSR (R1) advertises its locally assigned (incoming) labels to its LDP peer, A1, only when A1 requests them.
Example 2-32. LDP Distribution Protocol Neighbor Verification
R1#show mpls ldp neighbor
Peer LDP Ident: 10.10.20.101:1; Local LDP Ident 10.10.10.101:1
TCP connection: 10.10.20.2.38767 - 10.10.20.1.646
State: Oper; PIEs sent/rcvd: 371/366; ; Downstream on demand
Up time: 05:04:40
LDP discovery sources:
ATM2/0.1
_____________________________________________________________________
A1#show mpls ldp neighbor
Peer LDP Ident: 10.10.20.102:2; Local LDP Ident 10.10.20.101:2
TCP connection: 10.10.20.6.11002 - 10.10.20.5.646
State: Oper; PIEs sent/rcvd: 28096/28083; ; Downstream on demand
Up time: 2w3d
LDP discovery sources:
ATM1/0/1
Peer LDP Ident: 10.10.10.101:1; Local LDP Ident 10.10.20.101:1
TCP connection: 10.10.20.1.646 - 10.10.20.2.38767
State: Oper; PIEs sent/rcvd: 365/369; ; Downstream on demand
Up time: 05:03:28
LDP discovery sources:
ATM1/0/0
| Step 5. | Verify OSPF routing table on R4, as shown in Example 2-33.
Example 2-33. Verify OSPF Routing
R1#show ip route ospf
10.0.0.0/8 is variably subnetted, 7 subnets, 2 masks
O 10.10.20.4/30 [110/2] via 10.10.20.2, 05:51:42, ATM2/0.1
O 10.10.20.8/30 [110/3] via 10.10.20.2, 05:51:42, ATM2/0.1
O 10.10.10.104/32 [110/4] via 10.10.20.2, 05:51:42, ATM2/0.1
O 10.10.20.101/32 [110/2] via 10.10.20.2, 05:51:42, ATM2/0.1
O 10.10.20.102/32 [110/3] via 10.10.20.2, 05:51:42, ATM2/0.1
| Step 6. | Issue ping to 10.10.10.104 from R1 to ensure reachability, as displayed in Example 2-34.
Example 2-34. Verify Reachability
R1#ping 10.10.10.104
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.104, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
|
Control and Data Forwarding Operation in Basic Cell-Mode MPLS Configuration
Figure 2-10 shows the control and data plane forwarding operation in cell-mode MPLS.
Control Plane Operation in Basic Cell-Mode MPLS Configuration
The control plane operation shows the label propagation for prefix 10.10.10.101/32 from R1 to R4. The following steps are performed in the label propagation process for prefix 10.10.10.101/32:
Step 1. | Edge ATM LSR R4 requests a label for the 10.10.10.101/32 prefix using the LDP label mapping request from its downstream neighbor, ATM LSR A2. A2 requests a label for the 10.10.10.101/32 prefix using the LDP label mapping request from its downstream neighbor, ATM LSR A1. A1 in turn requests a label for the 10.10.10.101/32 prefix using the LDP label mapping request from its downstream neighbor, Edge ATM LSR R1. Edge ATM LSR R1 allocates a label to 10.10.10.101/32, which corresponds to its inbound VPI/VCI value 1/34, modifies the entry in the LFIB corresponding to 10.10.10.101/32, and sends it to A1 using an LDP reply. Example 2-35 shows the output of show mpls atm-ldp bindings.
Example 2-35. Label Allocation and Distribution Verification on R1
R1#show mpls forwarding-table
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
18 1/35 10.10.10.104/32 0 AT2/0.1 point2point
25 1/37 10.10.20.8/30 0 AT2/0.1 point2point
26 1/36 10.10.20.4/30 0 AT2/0.1 point2point
27 1/38 10.10.20.101/32 0 AT2/0.1 point2point
28 1/39 10.10.20.102/32 0 AT2/0.1 point2point
_____________________________________________________________________
R1#show mpls atm-ldp bindings
Destination: 10.10.10.104/32
Headend Router ATM2/0.1 (3 hops) 1/35 Active, VCD=19
Destination: 10.10.20.4/30
Headend Router ATM2/0.1 (1 hop) 1/36 Active, VCD=13
Destination: 10.10.20.8/30
Headend Router ATM2/0.1 (2 hops) 1/37 Active, VCD=15
Destination: 10.10.20.101/32
Headend Router ATM2/0.1 (1 hop) 1/38 Active, VCD=14
Destination: 10.10.20.102/32
Headend Router ATM2/0.1 (2 hops) 1/39 Active, VCD=16
Destination: 10.10.10.101/32
Tailend Router ATM2/0.1 1/34 Active, VCD=18
| Step 2. | A1 uses the VPI/VCI 1/34 received from R1 as its outbound VPI/VCI value, allocates a free VC that is mapped to the local inbound VPI/VCI 1/45, and modifies the LFIB entry for 10.10.10.101/32. A1 then sends VPI/VCI value 1/45 to A2 via an LDP reply. Example 2-36 shows the output of show mpls atm-ldp bindings. ATM LSR A1 prefix 10.10.10.104/32 has been assigned a local tag of 1/35 and an outgoing tag of 1/43. The outgoing tag is received from the downstream ATM LSR A2. During label distribution, the local tag of 1/35 has been propagated upstream to Router R1, which functions as the outgoing tag for the specific prefix 10.10.10.104/32 on R1.
Example 2-36. Label Allocation and Distribution Verification on A1
A1#show mpls atm-ldp bindings
Destination: 10.10.20.101/32
Tailend Switch ATM1/0/1 1/42 Active -> Terminating Active
Tailend Switch ATM1/0/0 1/38 Active -> Terminating Active
Destination: 10.10.20.0/30
Tailend Switch ATM1/0/1 1/43 Active -> Terminating Active
Destination: 10.10.10.104/32
Transit ATM1/0/0 1/35 Active -> ATM1/0/1 1/43 Active
Destination: 10.10.20.4/30
Tailend Switch ATM1/0/0 1/36 Active -> Terminating Active
Destination: 10.10.20.8/30
Transit ATM1/0/0 1/37 Active -> ATM1/0/1 1/44 Active
Destination: 10.10.20.102/32
Transit ATM1/0/0 1/39 Active -> ATM1/0/1 1/45 Active
Destination: 10.10.10.101/32
Transit ATM1/0/1 1/45 Active -> ATM1/0/0 1/34 Active
| Step 3. | A2 uses the VPI/VCI 1/45 received from A1 as its outbound VPI/VCI value, allocates a free VC that is mapped to the local inbound VPI/VCI 1/44, and modifies the LFIB entry for 10.10.10.101/32. A2 then sends VPI/VCI value 1/44 to R2 via an LDP reply. Example 2-37 shows the output of show mpls atm-ldp bindings. As shown in Example 2-37, ATM LSR A2 prefix 10.10.10.104/32 has been assigned a local tag of 1/43 and an outgoing tag of 1/35. The outgoing tag is received from the downstream Router R4. The local tag of 1/43 is propagated upstream to ATM LSR A1 and functions as the next-hop tag or outgoing tag for prefix 10.10.10.104/32 on ATM LSR A1.
Example 2-37. Label Allocation and Distribution Verification on A2
A2#show mpls atm-ldp bindings
Destination: 10.10.20.4/30
Tailend Switch ATM1/0/0 1/33 Active -> Terminating Active
Destination: 10.10.20.101/32
Transit ATM1/0/0 1/34 Active -> ATM1/0/1 1/42 Active
Destination: 10.10.20.102/32
Tailend Switch ATM1/0/0 1/35 Active -> Terminating Active
Tailend Switch ATM1/0/1 1/45 Active -> Terminating Active
Destination: 10.10.20.0/30
Transit ATM1/0/0 1/36 Active -> ATM1/0/1 1/43 Active
Destination: 10.10.10.104/32
Transit ATM1/0/1 1/43 Active -> ATM1/0/0 1/35 Active
Destination: 10.10.20.8/30
Tailend Switch ATM1/0/1 1/44 Active -> Terminating Active
Destination: 10.10.10.101/32
Transit ATM1/0/0 1/44 Active -> ATM1/0/1 1/45 Active
| Step 4. | Edge ATM LSR R2 uses VPI/VCI value 1/44 received from A2 as its outbound VPI/VCI value and modifies the entry in the LFIB. Example 2-38 shows the output of show mpls atm-ldp bindings. As shown in Example 2-38 on Edge ATM LSR R2, the mpls atm-ldp bindings show the local tag of 1/35 assigned to prefix 10.10.10.104/32. This local tag is propagated upstream to ATM LSR A2 and functions as the next-hop tag or outgoing tag for prefix 10.10.10.104/32 on A2.
Example 2-38. Label Allocation and Distribution Verification on R2
R2#show mpls forwarding-table
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
16 1/36 10.10.20.0/30 0 AT2/0.1 point2point
17 1/33 10.10.20.4/30 0 AT2/0.1 point2point
18 1/44 10.10.10.101/32 0 AT2/0.1 point2point
19 1/34 10.10.20.101/32 0 AT2/0.1 point2point
20 1/35 10.10.20.102/32 0 AT2/0.1 point2point
_____________________________________________________________________
R2#show mpls atm-ldp bindings
Destination: 10.10.20.0/30
Headend Router ATM2/0.1 (2 hops) 1/36 Active, VCD=16
Destination: 10.10.20.4/30
Headend Router ATM2/0.1 (1 hop) 1/33 Active, VCD=13
Destination: 10.10.20.101/32
Headend Router ATM2/0.1 (2 hops) 1/34 Active, VCD=15
Destination: 10.10.20.102/32
Headend Router ATM2/0.1 (1 hop) 1/35 Active, VCD=14
Destination: 10.10.10.101/32
Headend Router ATM2/0.1 (3 hops) 1/44 Active, VCD=18
Destination: 10.10.10.104/32
Tailend Router ATM2/0.1 1/35 Active, VCD=14
|
Data Forwarding Operation in Basic Cell-Mode MPLS Configuration
The following steps are performed in the data forwarding path from R4 to prefix 10.10.10.101/32:
Step 1. | R4 imposes label 1/44 on the AAL5 cell originating from R4 and destined to 10.10.10.101/32.
| Step 2. | A2 does an LFIB lookup and swaps label 1/44 with 1/45 and forwards that AAL5 cell to A1.
| Step 3. | A1 receives the data packet from A2, does an LFIB lookup, swaps label 1/45 with 1/34, and forwards that AAL5 cell to R1. Penultimate hop popping is not supported on ATM devices because the label is part of the ATM cell payload and cannot be removed by ATM switching hardware. Therefore, A1, which is an ATM device, does not perform any penultimate hop popping function.
|
Final Device Configurations for Basic Cell-Mode MPLS
Example 2-39 through Example 2-42 outline the pertinent configurations for all the devices in the cell-mode MPLS domain.
Example 2-39. R1 Configuration
hostname R1
!
ip cef
!
interface Loopback0
ip address 10.10.10.101 255.255.255.255
!
interface ATM2/0
!
interface ATM2/0.1 mpls
description Connection to A1
ip address 10.10.20.1 255.255.255.252
mpls ip
!
router ospf 100
log-adjacency-changes
network 10.10.0.0 0.0.255.255 area 0
Example 2-40. A1 Configuration
hostname A1
!
interface ATM1/0/0
description Connection to R1
ip address 10.10.20.2 255.255.255.252
mpls ip
!
interface ATM1/0/1
description Connection to A2
ip address 10.10.20.5 255.255.255.252
mpls ip
!
router ospf 100
network 10.10.0.0 0.0.255.255 area 0
Example 2-41. A2 Configuration
hostname A2
!
interface ATM1/0/0
description connection to R2
ip address 10.10.20.9 255.255.255.252
mpls ip
!
interface ATM1/0/1
description connection to A1
ip address 10.10.20.6 255.255.255.252
mpls ip
!
router ospf 100
network 10.10.0.0 0.0.255.255 area 0
!
Example 2-42. R2 Configuration
hostname R2
!
ip cef
!
interface Loopback0
ip address 10.10.10.104 255.255.255.255
!
interface ATM2/0
!
interface ATM2/0.1 mpls
description connection to A2
ip address 10.10.20.10 255.255.255.252
mpls ip
!
router ospf 100
log-adjacency-changes
network 10.10.0.0 0.0.255.255 area 0
Configuring Cell-Mode MPLS with VC-Merge
The VC-merge feature in cell-mode MPLS allows an ATM LSR to aggregate multiple incoming flows with the same destination address into a single outgoing flow. Therefore, when two Edge LSRs are sending packets to the same destination, the ingress label mapping to the two Edge LSRs are mapped to a single outgoing label. The number of VCs required for label switching is greatly reduced as the ATM switch maintains just one outgoing VC label for each destination prefix. VC-merge reduces the label space that needs to be maintained by sharing labels for flows toward the same FEC or prefix.
Figure 2-11 shows a cell-mode MPLS network. This is the same as the network shown in Figure 2-10 except the new Router R3 is added, which is connected to A1. Edge LSRs R1 and R3 share the same label space for the same destination prefixes on Edge ATM LSR R2.
Configuration Flowchart for Cell-Mode MPLS with VC-Merge
The configuration flowchart for Edge ATM LSR for cell-mode MPLS with VC-merge remains the same as what was shown for basic cell-mode MPLS (refer to Figure 2-8). The only difference in the basic cell-mode MPLS configuration block and cell-mode MPLS with VC-merge for ATM LSR is the inclusion of the command shown in Example 2-43.
Example 2-43. Enabling ATM VC-Merge
A1(config)#mpls ldp atm vc-merge
Depending upon the hardware, the ATM VC-merge capability is enabled by default; otherwise, this feature is disabled. Please check Cisco Documentation at cisco.com.
Configuration Steps for Cell-Mode MPLS with VC-Merge on Edge ATM LSR
The configuration steps for cell-mode MPLS with VC-merge on Edge ATM LSR are the same as what was shown earlier in section "Configuration Steps for Edge ATM LSR."
Configuration Steps for Cell-Mode MPLS with VC-Merge on ATM LSR
The configuration steps for cell-mode MPLS with VC-merge on ATM LSR are the same as those shown in the section "Configuration Steps for ATM LSR," except that A1 is enabled with the VC-merge command mpls ldp atm vc-merge.
Final Configuration for Devices in Cell-Mode MPLS with VC-Merge
The configurations for R1, R2, and A2 remain the same as what was shown in the section "Final Device Configurations for Basic Cell-Mode MPLS." The configurations for R3 and A1 are shown in Example 2-44 and Example 2-45. Note that the configuration for A1 does not depict the mpls ldp atm vc-merge command, which implies that the ATM LSR A1 supports VC-merge functionality by default.
Example 2-44. R3 Configuration (Truncated)
hostname R3
!
ip cef
!
interface Loopback0
ip address 10.10.10.105 255.255.255.255
!
interface ATM2/0
!
interface ATM2/0.1 mpls
description connection to A1
ip address 10.10.20.13 255.255.255.252
mpls ip
!
router ospf 100
network 10.10.0.0 0.0.255.255 area 0
Example 2-45. A1 Configuration (Truncated)
hostname A1
!
interface Loopback0
ip address 10.10.20.101 255.255.255.255
!
interface ATM1/0/0
description Connection to R1
ip address 10.10.20.2 255.255.255.252
mpls ip
!
interface ATM1/0/1
description Connection to A2
ip address 10.10.20.5 255.255.255.252
mpls ip
!
interface ATM1/0/2
description connection to R5
ip address 10.10.20.14 255.255.255.252
mpls ip
!
router ospf 100
network 10.10.0.0 0.0.255.255 area 0
Verification Steps for Cell-Mode MPLS with VC-Merge on ATM LSR
The following steps outline the verification procedure for cell-mode MPLS over ATM implementation with VC-merge on the ATM LSRs:
Step 1. | Verify if ATM VC-merge is enabled on the ATM LSR by issuing the show mpls atm-ldp capability command on the ATM LSR. The output of this command is shown in Example 2-46.
Example 2-46. ATM VC-Merge Capability
A1#show mpls atm-ldp capability
VPI VCI Alloc Odd/Even VC-Merge
ATM1/0/0 Range Range Scheme Scheme IN OUT
Negotiated [1 - 1] [33 - 16383] UNIDIR - -
Local [1 - 1] [33 - 16383] UNIDIR EN EN
Peer [1 - 1] [33 - 65530] UNIDIR - -
VPI VCI Alloc Odd/Even VC-Merge
ATM1/0/1 Range Range Scheme Scheme IN OUT
Negotiated [1 - 1] [33 - 16383] UNIDIR - -
Local [1 - 1] [33 - 16383] UNIDIR EN EN
Peer [1 - 1] [33 - 16383] UNIDIR
| Step 2. | When VC-merge is implemented on A1, destinations reachable by R1 and R3 via A1 are provided the same next-hop labels. When a lookup of the label bindings for prefixes on ATM LSR A1 is performed, the same outgoing label is used for two different incoming labels from two different flows that map to the same destination prefix. This is shown in Example 2-47. The ATM LSR A1 maps two incoming labels, 1/35 and 1/34, from Edge ATM LSRs R1 and R5, respectively, to the same outgoing label 1/43 for the destination prefix 10.10.10.104/32 located on R1.
Example 2-47. A1 VC-Merge Verification
A1#show mpls atm-ldp bindings 10.10.10.104 255.255.255.255
Destination: 10.10.10.104/32
Transit ATM1/0/0 1/35 Active -> ATM1/0/1 1/43 Active
Transit ATM1/0/2 1/34 Active -> ATM1/0/1 1/43 Active
|
Configuring MPLS Over ATM Without VC-Merge
In MPLS over ATM without VC-merge, each path (with the same ingress router and same Forwarding Equivalent Class [FEC]) consumes one label VC on each interface along the path. This results in unnecessary exhaustion of the already scarce label space.
The network topology remains the same as what was shown in the section "Configuring Cell-Mode MPLS with VC-Merge." All configurations remain the same except, as shown in Figure 2-11, where VC-merge is disabled on A1. Example 2-48 highlights the configuration to disable VC-merge.
Example 2-48. Disabling VC-Merge on A1
A1(config)#no mpls ldp atm vc-merge
Verify MPLS Over ATM Without VC-Merge
As shown in Example 2-49, when VC-merge is disabled on ATM LSR A1, flows to the same destination are assigned different outgoing VC labels. show mpls atm-ldp bindings on A1 shows two different outgoing labels, 1/33 and 1/36, are assigned to the data flows from R3 and R1, respectively, to destination prefix 10.10.10.104/32. Because VC-merge is not used, one VC is allocated per route as determined by the prefix in the routing table.
Example 2-49. A1: Disabled VC-Merge Verification
A1#show mpls atm-ldp bindings 10.10.10.104 255.255.255.255
Destination: 10.10.10.104/32
Transit ATM1/0/2 1/34 Active -> ATM1/0/1 1/33 Active
Transit ATM1/0/0 1/33 Active -> ATM1/0/1 1/36 Active
MPLS Over VP Tunnels Configuration and Verification
A VP tunnel is a method of linking two private ATM networks across a public network that does not support SVCs. The VP tunnel provides a permanent path through the public network. VP tunnels are multiplexing/demultiplexing multiple VCs from multiple interfaces, or from the same interface, to the VP tunnel interface. When multiplexing, it changes the VPI field of VCs that goes through the VP to the same as the VPI number on the VPs. VCI numbers, though, can be arbitrary. However, for specific VCs, the VCI numbers on both VP tunnel interfaces (originating and terminating) need to be the same. In this section, you configure VP tunnels on the ATM switches to carry label information for MPLS over ATM VP tunnels. Figure 2-12 shows an MPLS network using VP tunnels.
Configuration Flowchart for MPLS over VP Tunnels on Edge ATM LSR
The basic configuration flowchart for MPLS over VP tunnel is the same as what was shown in the section "Basic Cell-Mode MPLS Configuration and Verification" (refer to Figure 2-8).
Configuration Flowchart for Creating an ATM PVP on ATM Switch
The configuration flowchart for creating an ATM PVP is shown in Figure 2-13.
Configuration Steps for MPLS over VP Tunnels
Ensure necessary IP addresses are configured prior to following these steps. The steps to configure MPLS over VP tunnels are as follows:
Step 1. | A VP connection is like a bundle of VCs, transporting all cells with a common VPI, rather than a specific VPI and VCI. A PVP is a permanent VP (like PVC). Example 2-50 shows how to configure the internal cross-connect (within the switch router) PVP on switch A1 between interface 1/0/0, VPI = 2 and interface 1/0/1, VPI = 2, and switch A2 between interface 1/0/0, VPI = 2 and interface 1/0/1, VPI = 2.
Example 2-50. Configure VP Tunnels on ATM Switches
A1(config)#interface ATM1/0/1
A1(config-if)# description Connection to A2
A1(config-if)# no ip address
A1(config-if)# atm pvp 2 interface ATM1/0/0 2
_____________________________________________________________________
A2(config)#interface ATM1/0/1
A2(config-if)# description connection to A1
A2(config-if)# no ip address
A2(config-if)# atm pvp 2 interface ATM1/0/0 2
| Step 2. | Configure the VP tunnel using mpls atm vp-tunnel vpi vc-range { start-of-vci-range- end-of-vci-range} under the MPLS ATM subinterface. Enable MPLS on the created subinterface, as shown in Example 2-51.
Example 2-51. Configure VP Tunnel on ATM MPLS Subinterface
R1(config)#interface ATM2/0.1 mpls
R1(config-subif)# description Connection to A1
R1(config-subif)# ip address 10.10.20.1 255.255.255.252
R1(config-subif)# mpls atm vp-tunnel 2 vci-range 33-65535
R1(config-subif)#mpls ip
_____________________________________________________________________
R2(config)#interface ATM2/0.1 mpls
R2(config-subif)# description connection to A2
R2(config-subif)# ip address 10.10.20.2 255.255.255.252
R2(config-subif)# mpls atm vp-tunnel 2 vci-range 33-65535
R2(config-subif)#mpls ip
| Step 3. | Configure IGP for IP connectivity across the VP tunnel on R1 and R2, as shown in Example 2-52.
Example 2-52. Configure IGP
R1(config)#router ospf 100
R1(config-router)# network 10.10.0.0 0.0.255.255 area 0
|
Verification Steps for MPLS over VP Tunnels
The steps to verify MPLS over VP tunnels are as follows:
Step 1. | Verify operation of PVP on the ATM switches, as shown in Example 2-53.
Example 2-53. Verify PVP Status
A1#show atm vp
Interface VPI Type X-Interface X-VPI Status
ATM1/0/0 2 PVP ATM1/0/1 2 UP
ATM1/0/1 2 PVP ATM1/0/0 2 UP
_____________________________________________________________________
A2#show atm vp
Interface VPI Type X-Interface X-VPI Status
ATM1/0/0 2 PVP ATM1/0/1 2 UP
ATM1/0/1 2 PVP ATM1/0/0 2 UP
| Step 2. | Verify OSPF routes on R1 by issuing show ip route ospf. Example 2-54 shows the networks received on R1 from R2.
Example 2-54. Verify OSPF Routes
R1#show ip route ospf
10.0.0.0/8 is variably subnetted, 7 subnets, 2 masks
O 10.10.20.2/32 [110/1] via 10.10.20.2, 00:12:25, ATM2/0.1
O 10.10.10.104/32 [110/2] via 10.10.20.2, 00:12:25, ATM2/0.1
O 10.10.20.128/30 [110/11] via 10.10.20.2, 00:12:25, ATM2/0.1
| Step 3. | Verify connectivity across the VP tunnel using the ping command, as shown in Example 2-55.
Example 2-55. Verify Connectivity Using Ping
R1#ping ip 10.10.20.129 source 10.10.20.193
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.20.129, timeout is 2 seconds:
Packet sent with a source address of 10.10.20.193
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms
|
Final Device Configurations for MPLS over VP Tunnels
The final device configuration for R1, A1, A2, and R2 is shown in Example 2-56 through Example 2-59.
Example 2-56. R1 Configuration
hostname R1
!
ip cef
!
interface Loopback0
ip address 10.10.10.101 255.255.255.255
!
interface Ethernet0
ip address 10.10.20.193 255.255.255.252
!
interface ATM2/0
!
interface ATM2/0.1 mpls
description Connection to A1
ip address 10.10.20.1 255.255.255.252
mpls ip
mpls atm vp-tunnel 2 vci-range 33-65535
!
router ospf 100
network 10.10.0.0 0.0.255.255 area 0
Example 2-57. A1 Configuration
hostname A1
!
interface ATM1/0/0
description Connection to R1
!
interface ATM1/0/1
description Connection to A2
atm pvp 2 interface ATM1/0/0 2
!
Example 2-58. A2 Configuration
hostname A2
!
interface ATM1/0/0
description connection to R2
!
interface ATM1/0/1
description connection to A1
atm pvp 2 interface ATM1/0/0 2
!
Example 2-59. R2 Configuration
hostname R2
!
ip cef
!
interface Loopback0
ip address 10.10.10.104 255.255.255.255
!
interface Ethernet0
ip address 10.10.20.129 255.255.255.252
!
interface ATM2/0
!
interface ATM2/0.1 mpls
description connection to A2
ip address 10.10.20.10 255.255.255.252
mpls ip
mpls atm vp-tunnel 2 vci-range 33-65535
!
router ospf 100
network 10.10.0.0 0.0.255.255 area 0
Implementing Cell-Mode MPLS with BPX8600 and 7200 as Label Switch Controller
Cell-mode MPLS can also be implemented by separating the control and data plane functions of an ATM LSR. The control plane function is performed by a device called the LSC or label switch controller, and the data plane function can be performed by an ATM switch such as the BPX8600 Series ATM switches. In the BPX with LSC design, the LSC is connected to the BPX ATM switch by trunks that can carry PVCs, SVCs, or MPLS Label VCs (LVCs). The control software is physically located in the LSC that is connected to the ATM switch by a physical connection also called the virtual switch interface (VSI) control link. The VSI control link could be an STM-1 link connected to a single port of a broadband switching module (BXM) linecard on the BPX8600. This is shown in Figure 2-14.
In Figure 2-14, the functions control plane is implemented using a BPX+LSC. The figure outlines a connection from each of the Edge ATM LSRs to the LSC connected to the BPX switch using LVCs. These signaling LVCs are maintained per LSR that the BPX+LSC is connected to. In addition, VSI control links are maintained per card on the BPX.
From a data plane perspective, data label VCs bypass the LSC and are switched using the BPX ports. Therefore, in the data plane, the traffic via the ATM label switch router traverses only the BPX ATM switch and not the LSC.
The signaling label VCs are on VPI/VCI values of 0/32 by default and will be cross-connected to a different VCI on the switch control link between the BPX and LSC. One key thing to note is that the LSC functions as the VSI master and the BPX functions as the VSI slave.
Configuring BPX+LSC as ATM LSR
This section deals with the configuration of a BPX+LSC as an ATM LSR to implement cell-mode MPLS. The topology used to implement this configuration is shown in Figure 2-15.
Figure 2-15 shows the physical connections for this section in which two Edge ATM LSRs are connected to a BPX 8600 switch. The LSC (7200 router) is also connected on the same switch. The numbers 2.1, 2.2, and 2.3 in Figure 2-15 pertain to slot.port on the BPX 8600 switch. The only IP addresses shown in this figure are those of the loopbacks on the LSR and ELSRs. Figure 2-16 shows the Edge ATM LSRs connected to the LSC in the control plane using the VSI control VCs as well as the signaling LVCs that originate from an mpls subinterface on the Edge ATM LSR and terminate on an XtagATM interface on the LSC. The XtagATM interface controls the trunks on the BPX that are connected to other LSRs.
Configuring the BPX
The steps to configure the BPX are as follows:
Step 1. | Verify the cards on the BPX by issuing dspcds command. As shown in Example 2-60, the BXM-155 card connects and configures the trunks on the BPX as well as the appropriate resources on the ports.
Example 2-60. Viewing Cards on BPX
bpxa TRM cisco:1 BPX 8620 9.2.30 Oct. 8 2004 15:18 MST
FrontCard BackCard FrontCard BackCard
Type Rev Type Rev Status Type Rev Type Rev Status
1 BME-622 KMB SM-2 BD Standby 9 Empty
2 BXM-155 FJL MM-8 BB Active 10 Empty
3 BXM-T3 FJL TE3-12BA Active 11 Empty
4 BXM-622 FML SM-2 BD Standby 12 Empty
5 BXM-155 FAL SM-4 BB Standby 13 Empty
6 BXM-622 FPH SM-2 BE Standby 14 Empty
7 BCC-4 HDM LM-2 AC Active 15 ASM ACC LMASM AC Active
8 Empty reserved for Card
Last Command: dspcds
Next Command:
| Step 2. | Enable the trunks on the ports 2.1, 2.2, and 2.3. This is as shown in Example 2-60. Example 2-61 shows only the command to be used in the "next command" section to enable the three trunks connecting to the two Edge ATM LSRs as well as the LSC.
Example 2-61. Configuring Trunks on the BPX (Commands)
Next Command: uptrk 2.1
Next Command: uptrk 2.2
Next Command: uptrk 2.3
When the trunks are configured, view the trunk configuration using the dsptrks command, as shown in Example 2-62.
Example 2-62. Viewing Trunk Configuration
bpxa TRM cisco:1 BPX 8620 9.2.30 Oct. 8 2004 15:26 MST
TRK Type Current Line Alarm Status Other End
2.1 OC3 Clear - OK -
2.2 OC3 Clear - OK -
2.3 OC3 Clear - OK -
Last Command: dsptrks
Next Command:
| Step 3. | Configuration of resources applied to the trunks already configured is performed using the cnfrsrc command on the BPX, as shown in Example 2-63.
Example 2-63. Configuring Resources
bpxa TRM cisco:1 BPX 8620 9.2.30 Oct. 8 2004 15:29 MST
Port/Trunk : 2.1
Maximum PVC LCNS: 256 Maximum PVC Bandwidth:247207
(Statistical Reserve: 1000)
Partition 1
Partition State : Enabled
Minimum VSI LCNS: 600
Maximum VSI LCNS: 1500
Start VSI VPI: 240
End VSI VPI : 255
Minimum VSI Bandwidth : 105000 Maximum VSI Bandwidth : 105000
VSI ILMI Config : 0
VSI Topo Dsc : 0 VSI Ses Ctrlr Id : 255
Last Command: cnfrsrc 2.1 256 247207 y 1 e 600 1500 240 255 105000 105000
The command in Example 2-63 can be explained as "configure resources for trunk 2.1 where the maximum PVC LCNs are 256, the maximum PVC bandwidth is 247207; editing of VSI information is enabled, Partition ID is 1 and is enabled; the maximum VSI LCNs are 600 and the maximum VSI LCNs are 1500; the VSI VPI-range is configured to be between 240?55 and the minimum and maximum VSI bandwidths is 105000."
Repeat this command to configure resources for trunks 2.2 and 2.3. However, all trunks need to be part of the same partition (1). When completed, a dsprsrc issued for the appropriate trunk and partition IDs, as shown in Example 2-64, shows the resources allocated to the trunk.
Example 2-64. Display Configured Resources
bpxa TRM cisco:1 BPX 8620 9.2.30 Oct. 8 2004 15:37 MST
Port/Trunk : 2.2
Maximum PVC LCNS: 256 Maximum PVC Bandwidth:247207
(Statistical Reserve: 1000)
Partition 1
Partition State : Enabled
Minimum VSI LCNS: 512
Maximum VSI LCNS: 1500
Start VSI VPI: 240
End VSI VPI : 255
Minimum VSI Bandwidth : 105000 Maximum VSI Bandwidth : 105000
VSI ILMI Config : 0
VSI Topo Dsc : 0 VSI Ses Ctrlr Id : 255
Last Command: dsprsrc 2.2 1
| Step 4. | MPLS labeled packets use the queues 10?4 on each port (one queue per class). To enable MPLS packet forwarding, configure the queues using the cnfqbin command. Example 2-65 shows the command to configure the qbin 10 on BPX trunk 2.2 as well as the output of the configuration.
Example 2-65. Configuring Qbin's on BPX Ports for MPLS
bpxa TRM cisco:1 BPX 8620 9.2.30 Oct. 8 2004 15:43 MST
Qbin Database 2.2 on BXM qbin 10 (Configured by User)
(EPD Enabled on this qbin)
Qbin State: Enabled
Discard Threshold: 65536 cells
EPD Threshold: 95%
High CLP Threshold: 100%
EFCI Threshold: 40%
Last Command: cnfqbin 2.2 10 e n 65536 95 100 40
| Step 5. | Finally, add an LSC shelf as a VSI master using the addshelf command. In Example 2-66, the first "1" after "VSI" is the VSI controller ID, which must be set the same on both the BPX 8650 and the LSC. The default controller ID on the LSC is "1." The second "1" after "VSI" is the partition ID that indicates this is a controller for partition 1. The "v" stands for a VSI controller.
Example 2-66. Adding VSI Master Shelf
bpxa TRM cisco:1 BPX 8620 9.2.30 Oct. 8 2004 15:48 MST
BPX 8620 Interface Shelf Information
Trunk Name Type Part Id Ctrl Id Control_VC Alarm
VPI VCIRange
2.2 VSI VSI 1 1 0 40-54 OK
Last Command: addshelf 2.2 v 1 1 0 40
To verify, perform a dsptrks, and the trunk 2.2 appears with VSI on the other end column to show that a VSI master systems or device is connected on trunk 2.2, as shown in Example 2-67.
Example 2-67. Verification of VSI
a TRM cisco:1 BPX 8620 9.2.30 Oct. 8 2004 15:51 MST
TRK Type Current Line Alarm Status Other End
2.1 OC3 Clear - OK -
2.2 OC3 Clear - OK VSI(VSI)
2.3 OC3 Clear - OK -
|
Configuration of the Label Switch Controller
Configuration of the LSC involves enabling the 7200/7500 series as a LSC for the BPX shelf and configuration of XTagATM interfaces to control the trunks on the BPX shelf:
Step 1. | Configure the ATM interface connected to the BPX trunk 2.2 to be the VSI control link between the BPX and the 7200/7500. See Example 2-68.
Example 2-68. Configure 7200/7500 Port as a LSC Port
LSC(config)#interface ATM1/0
LSC(config-if)# no ip address
LSC(config-if)# tag-control-protocol vsi
| Step 2. | Configure the XTagATM interfaces as control links for the trunks 2.1 and 2.3 on the BPX using the extended port command on the LSC, as displayed in Example 2-69. Note that the numbering of the XTagATM interfaces maps to the actual trunk ports that they control on the BPX shelf. Therefore, XTagATM interface 21 controls BPX trunk 2.1, and XTagATM interface 23 controls BPX trunk 2.3.
Example 2-69. Configure Control Links Using XTagATM Interfaces on LSC
LSC(config)#interface ATM1/0
LSC(config-if)# no ip address
LSC(config-if)# tag-control-protocol vsi
LSC(config-if)#interface XTagATM21
LSC(config-if)# ip address 10.10.10.2 255.255.255.252
LSC(config-if)# extended-port ATM1/0 bpx 2.1
LSC(config-if)# mpls ip
LSC(config-if)#interface XTagATM23
LSC(config-if)# ip address 10.10.10.6 255.255.255.252
LSC(config-if)# extended-port ATM1/0 bpx 2.3
LSC(config-if)# mpls ip
| Step 3. | Configure OSPF as the IGP on the LSC, and include all interfaces for OSPF routing. See Example 2-70.
Example 2-70. Configure IGP (OSPF) on LSC
LSC(config)#router ospf 100
LSC(config-router)# log-adjacency-changes
LSC(config-router)# network 10.10.10.0 0.0.0.255 area 0
| Step 4. | Verify the operation of the VSI control interfaces using the show controllers vsi status command on the LSC. See Example 2-71.
Example 2-71. Verify VSI Controller Status
LSC#show controllers vsi status
Interface Name IF Status IFC State Physical Descriptor
XTagATM21 up ACTIVE 0.2.1.0
switch control port n/a ACTIVE 0.2.2.0
XTagATM23 up ACTIVE 0.2.3.0
|
Configuration of Edge ATM LSRs
The configuration of the Edge ATM LSRs contains the same configuration as that of Edge ATM LSRs when implementing basic cell-mode MPLS, involving configuration of an MPLS subinterface under the ATM physical interface and other ATM-TDP parameters. OSPF is the IGP routing protocol. See Example 2-72.
Example 2-72. Configuration of Edge ATM LSR
ELSR1(config)#interface ATM3/0
ELSR1(config-if)# no ip address
ELSR1(config-if)#interface ATM3/0.1 mpls
ELSR1(config-subif)# ip address 10.10.10.1 255.255.255.252
ELSR1(config-subif)# mpls atm vpi 240-255
ELSR1(config-subif)# mpls ip
ELSR1(config)#router ospf 100
ELSR1(config-router)# router-id 10.10.10.101
ELSR1(config-router)# network 10.10.10.0 0.0.0.255 area 0
_____________________________________________________________________
ELSR2(config)#interface ATM1/0
ELSR2(config-if)# no ip address
ELSR2(config-if)#interface ATM1/0.1 mpls
ELSR2(config-subif)# ip address 10.10.10.5 255.255.255.252
ELSR2(config-subif)# mpls atm vpi 240-255
ELSR2(config-subif)# mpls ip
ELSR2(config-subif)#router ospf 100
ELSR2(config-router)# network 10.10.10.0 0.0.0.255 area 0
The key command to be added in Example 2-72 is mpls atm vpi, which defines the VPI range to be used for the LVCs. This needs to match the configuration of the BPX, as shown in Example 2-64.
Verification of Cell-Mode MPLS with BPX+LSC Operation
Step 1. | Verify TDP neighbor discovery and neighbor status on ELSR1, ELSR2, and LSC. Note that, because the LSC is only capable of ATM-TDP, the peering process appears as a TDP neighbor relationship and not a ATM-LDP neighbor relationship. See Example 2-73.
Example 2-73. TDP Neighbor Verification
ELSR1#show mpls ldp neighbor
Peer TDP Ident: 10.10.10.100:1; Local TDP Ident 10.10.10.101:1
TCP connection: 10.10.10.2.11375 - 10.10.10.1.711
State: Oper; PIEs sent/rcvd: 813/809; Downstream on demand
Up time: 11:39:02
TDP discovery sources:
ATM3/0.1, Src IP addr: 10.10.10.2
_____________________________________________________________________
ELSR1#show mpls ldp discovery
Local LDP Identifier:
10.10.10.101:0
Discovery Sources:
Interfaces:
ATM3/0.1 (tdp): xmit/recv
TDP Id: 10.10.10.100:1; IP addr: 10.10.10.2
_____________________________________________________________________
ELSR2#show mpls ldp neighbor
Peer TDP Ident: 10.10.10.100:2; Local TDP Ident 10.10.10.102:1
TCP connection: 10.10.10.6.11376 - 10.10.10.5.711
State: Oper; PIEs sent/rcvd: 813/813; Downstream on demand
Up time: 11:39:47
TDP discovery sources:
ATM1/0.1, Src IP addr: 10.10.10.6
_____________________________________________________________________
ELSR2#show mpls ldp discovery
Local LDP Identifier:
10.10.10.102:0
Discovery Sources:
Interfaces:
ATM1/0.1 (tdp): xmit/recv
TDP Id: 10.10.10.100:2; IP addr: 10.10.10.6
_____________________________________________________________________
LSC#show tag-switching tdp neighbor
Peer TDP Ident: 10.10.10.101:1; Local TDP Ident 10.10.10.100:1
TCP connection: 10.10.10.1.711 - 10.10.10.2.11375
State: Oper; PIEs sent/rcvd: 813/816; ; Downstream on demand
Up time: 11:42:08
TDP discovery sources:
XTagATM21
Peer TDP Ident: 10.10.10.102:1; Local TDP Ident 10.10.10.100:2
TCP connection: 10.10.10.5.711 - 10.10.10.6.11376
State: Oper; PIEs sent/rcvd: 816/815; ; Downstream on demand
Up time: 11:42:06
TDP discovery sources:
XTagATM23
_____________________________________________________________________
LSC#show tag-switching tdp discovery
Local TDP Identifier:
10.10.10.100:0
TDP Discovery Sources:
Interfaces:
XTagATM21: xmit/recv
TDP Id: 10.10.10.101:1; IP addr: 10.10.10.1
XTagATM23: xmit/recv
TDP Id: 10.10.10.102:1; IP addr: 10.10.10.5
| Step 2. | Verify MPLS label exchange on the Edge LSRs, as shown in Example 2-74.
Example 2-74. MPLS Label Mapping/Exchange Verification
ELSR1#show mpls atm-ldp bindings
Destination: 10.10.10.4/30
Headend Router ATM3/0.1 (1 hop) 240/38 Active, VCD=21
Destination: 10.10.10.100/32
Headend Router ATM3/0.1 (1 hop) 240/40 Active, VCD=22
Destination: 10.10.10.102/32
Headend Router ATM3/0.1 (2 hops) 240/42 Active, VCD=23
Destination: 10.10.10.101/32
Tailend Router ATM3/0.1 240/33 Active, VCD=19
Tailend Router ATM3/0.1 240/35 Active, VCD=20
_____________________________________________________________________
ELSR2#show mpls atm-ldp bindings
Destination: 10.10.10.0/30
Headend Router ATM1/0.1 (1 hop) 240/38 Active, VCD=22
Destination: 10.10.10.100/32
Headend Router ATM1/0.1 (1 hop) 240/40 Active, VCD=23
Destination: 10.10.10.101/32
Headend Router ATM1/0.1 (2 hops) 240/42 Active, VCD=24
Destination: 10.10.10.102/32
Tailend Router ATM1/0.1 240/33 Active, VCD=20
Tailend Router ATM1/0.1 240/35 Active, VCD=21
| Step 3. | Verify IGP connectivity, as illustrated in Example 2-75.
Example 2-75. Verification of IGP Connectivity
ELSR1#show ip route ospf
10.0.0.0/8 is variably subnetted, 6 subnets, 3 masks
O 10.10.10.4/30 [110/3] via 10.10.10.2, 12:14:50, ATM3/0.1
O 10.10.10.102/32 [110/4] via 10.10.10.2, 12:14:50, ATM3/0.1
O 10.10.10.100/32 [110/2] via 10.10.10.2, 12:14:50, ATM3/0.1
__________________________________________________________________________
ELSR2#show ip route ospf
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
O 10.10.10.0/30 [110/3] via 10.10.10.6, 12:15:17, ATM1/0.1
O 10.10.10.100/32 [110/2] via 10.10.10.6, 12:15:17, ATM1/0.1
O 10.10.10.101/32 [110/4] via 10.10.10.6, 12:15:17, ATM1/0.1
__________________________________________________________________________
LSC#show ip route ospf
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
O 10.10.10.102/32 [110/3] via 10.10.10.5, 12:15:37, XTagATM23
O 10.10.10.101/32 [110/3] via 10.10.10.1, 12:15:37, XTagATM21
| Step 4. | Confirm connectivity using ping between ELSRs, as shown in Example 2-76.
Example 2-76. Verification of Reachability
LSR1#ping 10.10.10.102
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.102, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4
|
|
