Configuring A Static Route To A Peer - Cisco CRS Configuration Manual

Implementing MPLS Layer 3 VPNs
Step 14
allowas-in [ as-occurrence-number]
Example:
RP/0/RP0/CPU0:router(config-bgp-vrf-nbr-af)# allowas-in 5
Allows an AS path with the PE autonomous system number (ASN) a specified number of times.
Hub and spoke VPN networks need the looping back of routing information to the HUB PE through the HUB CE. When
this happens, due to the presence of the PE ASN, the looped-back information is dropped by the HUB PE. To avoid this,
use the allowas-in command to allow prefixes even if they have the PEs ASN up to the specified number of times.
Step 15
Use the commit or end command.
commit - Saves the configuration changes and remains within the configuration session.
end - Prompts user to take one of these actions:
• Yes - Saves configuration changes and exits the configuration session.
• No - Exits the configuration session without committing the configuration changes.
• Cancel - Remains in the configuration mode, without committing the configuration changes.

Configuring a Static Route to a Peer

Perform this task to configure a static route to an Inter-AS or CSC-CE peer.
When you configure an Inter-AS or CSC peer, BGP allocates a label for a /32 route to that peer and performs
a NULL label rewrite. When forwarding a labeled packet to the peer, the router removes the top label from
the label stack; however, in such an instance, BGP expects a /32 route to the peer. This task ensures that there
is, in fact, a /32 route to the peer.
Please be aware of the following facts before performing this task:
• A /32 route is not required to establish BGP peering. A route using a shorter prefix length will also work.
• A shorter prefix length route is not associated with the allocated label; even though the BGP session
To configure a static route on a CSC-PE, you must configure the router under the VRF (as noted in the
Note
detailed steps).
SUMMARY STEPS
1. configure
2. router static
3. address-family ipv4 unicast
4. A.B.C.D/length next-hop
5. Use the commit or end command.
comes up between the peers, without the static route, forwarding will not work.
Cisco IOS XR Virtual Private Network Configuration Guide for the Cisco CRS Router, Release 6.1.x
Configuring Carrier Supporting Carrier
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