For LDP-signaled pseudowires, including L2CIRCUIT and VPLS, a redundant pseudowire can act as a backup connection between PE routers and CE devices, thus maintaining Layer 2 circuit and VPLS services after certain types of failures. This feature can help improve the reliability of certain types of networks where a single point of failure could interrupt service for multiple customers.
This article demonstrates with an example how the redundant pseudowire feature can be configured on MX Series routers.
Note: Redundant pseudowires cannot reduce traffic loss to zero. However, they provide a way to gracefully recover from pseudowire failures such that services can be restarted within a known time limit.
When you configure redundant pseudowires to remote PE routers, you configure one to act as the primary pseudowire over which customer traffic will be transmitted and you configure another to act as the backup pseudowire in the event that the primary fails. You configure the two pseudowires statically, and allocate a separate label for the primary and backup neighbors.
Topology
+-------+
| R2 |ge-1/2/1
+------------+ PE2 +-------------+
| +---+---+ |
| | |ge-1/3/1
+-----+ +---+---+ | +--------+ +--------+
| | ge-1/2/0| R1 | | | |ge-1/2/3 | |
| CE1 +-----------+ PE1 | | | SW +-------------+ CE2 |
+-----+ge-1/3/0 +---+---+ | +--------+ ge-1/3/3+--------+
10.0.0.1/24 | +---+---+ |ge-1/3/2 10.0.0.2/24
| | R3 | |
+------------+ PE3 +-------------+
+-------+ge-1/2/2
In the above topology:
- R1: 1.1.1.1
- R2: 2.2.2.2
- R3: 3.3.3.3
- OSPF/LDP in the MPLS core between R1/R2/R3
- CE1: 10.0.0.1/24
- CE2: 10.0.0.2/24
Configuration
R1/R2/R3> show configuration interfaces ge-x/x/x
unit 100 {
encapsulation vlan-vpls;
vlan-id 100;
family vpls;
}
R1> show configuration routing-instances
test {
instance-type vpls;
interface ge-1/2/0.100;
protocols {
vpls {
encapsulation-type ethernet-vlan;
interface ge-1/2/0.100;
no-tunnel-services;
vpls-id 100;
mtu 9192;
neighbor 2.2.2.2 {
backup-neighbor 3.3.3.3;
}
}
}
}
R2> show configuration routing-instances
test {
instance-type vpls;
interface ge-1/2/1.100;
protocols {
vpls {
encapsulation-type ethernet-vlan;
interface ge-1/2/1.100;
no-tunnel-services;
vpls-id 100;
mtu 9192;
neighbor 1.1.1.1;
}
}
}
R3> show configuration routing-instances
test {
instance-type vpls;
interface ge-1/2/2.100;
protocols {
vpls {
encapsulation-type ethernet-vlan;
interface ge-1/2/2.100;
no-tunnel-services;
vpls-id 100;
mtu 9192;
neighbor 1.1.1.1;
}
}
}
Output / Verification
R1> show vpls connections
Layer-2 VPN connections:
Legend for connection status (St)
EI -- encapsulation invalid NC -- interface encapsulation not CCC/TCC/VPLS
EM -- encapsulation mismatch WE -- interface and instance encaps not same
VC-Dn -- Virtual circuit down NP -- interface hardware not present
CM -- control-word mismatch -> -- only outbound connection is up
CN -- circuit not provisioned <- -- only inbound connection is up
OR -- out of range Up -- operational
OL -- no outgoing label Dn -- down
LD -- local site signaled down CF -- call admission control failure
RD -- remote site signaled down SC -- local and remote site ID collision
LN -- local site not designated LM -- local site ID not minimum designated
RN -- remote site not designated RM -- remote site ID not minimum designated
XX -- unknown connection status IL -- no incoming label
MM -- MTU mismatch MI -- Mesh-Group ID not available
BK -- Backup connection ST -- Standby connection
PF -- Profile parse failure PB -- Profile busy
RS -- remote site standby SN -- Static Neighbor
LB -- Local site not best-site RB -- Remote site not best-site
VM -- VLAN ID mismatch HS -- Hot-standby Connection
Legend for interface status
Up -- operational
Dn -- down
Instance: test
VPLS-id: 100
Neighbor Type St Time last up # Up trans
2.2.2.2(vpls-id 100) rmt Up Aug 5 08:01:27 2019 1 <<<<<<Primary neighbor>>>>>>
Remote PE: 2.2.2.2, Negotiated control-word: No
Incoming label: 262145, Outgoing label: 262145
Negotiated PW status TLV: No
Local interface: lsi.118489088, Status: Up, Encapsulation: VLAN
Description: Intf - vpls test neighbor 2.2.2.2 vpls-id 100
Flow Label Transmit: No, Flow Label Receive: No
3.3.3.3(vpls-id 100) rmt BK <<<Backup neighbor. In "Backup connection" status>>>>
R2> show vpls connections
<SNIP>
Instance: test
VPLS-id: 100
Neighbor Type St Time last up # Up trans
1.1.1.1(vpls-id 100) rmt Up Aug 5 08:01:27 2019 1 <<<<<<primary neighbor>>>>>>
Remote PE: 1.1.1.1, Negotiated control-word: No
Incoming label: 262145, Outgoing label: 262145
Negotiated PW status TLV: No
Local interface: lsi.68157440, Status: Up, Encapsulation: VLAN
Description: Intf - vpls test neighbor 1.1.1.1 vpls-id 100
Flow Label Transmit: No, Flow Label Receive: No
R3> show vpls connections
<SNIP>
Instance: test
VPLS-id: 100
Neighbor Type St Time last up # Up trans
1.1.1.1(vpls-id 100) rmt OL <<<<<<backup neighbor. In "no outgoing label" status>>>>>>
R3> show interfaces ge-1/2/2 <<<<<<On backup PE, CE facing interface is up. Loop prevention done on core side>>>>>>
<<<<<<This is different from BGP signaled VPLS Multihoming, where interface is ccc-down>>>>>>
Logical interface ge-1/2/2.100 (Index 413) (SNMP ifIndex 673)
Flags: Up SNMP-Traps 0x0 VLAN-Tag [ 0x8100.100 ] Encapsulation: VLAN-VPLS
Input packets : 12
Output packets: 0
Protocol vpls, MTU: 1522
Flags: Is-Primary
ce1> ping 10.0.0.2 <<<<<<ping between CEs works fine>>>>>>
PING 10.0.0.2 (10.0.0.2): 56 data bytes
64 bytes from 10.0.0.2: icmp_seq=0 ttl=64 time=47.888 ms
64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=0.741 ms
64 bytes from 10.0.0.2: icmp_seq=2 ttl=64 time=0.853 ms
64 bytes from 10.0.0.2: icmp_seq=3 ttl=64 time=0.841 ms
^C
--- 10.0.0.2 ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.741/12.581/47.888/20.385 ms
sw> show bridge mac-table
Logical system : sw
Routing instance : default
Bridging domain : v100, VLAN : 100
MAC MAC Logical NH MAC active
address flags interface Index property source
80:71:1f:c1:21:90 D ge-1/3/1.100 <<<<<<CE1 MAC learned from R2, primary neighbor>>>>>>
80:71:1f:c1:21:93 D ge-1/2/3.100
Other Parameter Options
R1#set routing-instances test protocols vpls neighbor 2.2.2.2 backup-neighbor 3.3.3.3 standby
Configures the pseudowire to the specified backup neighbor as the standby. When you configure this statement, traffic flows over both the active and standby pseudowires to the CE device. The CE device drops the traffic from the standby pseudowire, unless the active pseudowire fails. If the active pseudowire fails, the CE device automatically switches to the standby pseudowire.
R1>show vpls connections
<SNIP>
Instance: test
VPLS-id: 100
Neighbor Type St Time last up # Up trans
2.2.2.2(vpls-id 100) rmt Up Aug 5 08:01:27 2019 1
Remote PE: 2.2.2.2, Negotiated control-word: No
Incoming label: 262145, Outgoing label: 262145
Negotiated PW status TLV: No
Local interface: lsi.118489088, Status: Up, Encapsulation: VLAN
Description: Intf - vpls test neighbor 2.2.2.2 vpls-id 100
Flow Label Transmit: No, Flow Label Receive: No
3.3.3.3(vpls-id 100) rmt ST <<<<<<backup neighbor in "Standby connection" mode>>>>>>
R3> show vpls connections
<SNIP>
Instance: test
VPLS-id: 100
Neighbor Type St Time last up # Up trans
1.1.1.1(vpls-id 100) rmt Up Aug 5 08:11:43 2019 1 <<<<<<backup neighbor comes up>>>>>>
Remote PE: 1.1.1.1, Negotiated control-word: No
Incoming label: 262145, Outgoing label: 262146
Negotiated PW status TLV: No
Local interface: lsi.84934656, Status: Up, Encapsulation: VLAN
Description: Intf - vpls test neighbor 1.1.1.1 vpls-id 100
Flow Label Transmit: No, Flow Label Receive: No
R1#set routing-instances test protocols vpls neighbor 2.2.2.2 switchover-delay 5000
After the primary pseudowire goes down, switchover-delay specifies the delay (in milliseconds) to wait before the backup pseudowire takes over. The default is 10,000 milliseconds.
R1#set routing-instances test protocols vpls neighbor 2.2.2.2 revert-time 60
With this option, you can specify a revert time for the redundant pseudowires when the primary neighbor comes back up from failure. Without the revert-time statement, by default, the virtual circuit (VC) traffic is not transitioned to the primary path upon restoration of the primary path.