Indicate Bgp Back-Door Routes - Cisco NCS 5500 Series Configuration Manual

Indicate BGP Back-door Routes

SUMMARY STEPS
1. configure
2. router bgp as-number
3. address-family { ipv4 | ipv6 } unicast
4. distance bgp external-distance internal-distance local-distance
5. commit
DETAILED STEPS
Step 1 configure
Step 2
router bgp as-number
Example:
RP/0/RP0/CPU0:router(config)# router bgp 120
Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP
routing process.
Step 3 address-family { ipv4 | ipv6 } unicast
Example:
RP/0/RP0/CPU0:router(config-bgp)# address-family ipv4 unicast
Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.
To see a list of all the possible keywords and arguments for this command, use the CLI help (?).
Step 4 distance bgp external-distance internal-distance local-distance
Example:
RP/0/RP0/CPU0:router(config-bgp-af)# distance bgp 20 20 200
Sets the external, internal, and local administrative distances to prefer one class of routes over another. The higher the
value, the lower the trust rating.
Step 5 commit
Indicate BGP Back-door Routes
In most cases, when a route is learned through eBGP, it is installed in the IP routing table because of its
distance. Sometimes, however, two ASs have an IGP-learned back-door route and an eBGP-learned route.
Their policy might be to use the IGP-learned path as the preferred path and to use the eBGP-learned path
when the IGP path is down.
Perform this task to set the administrative distance on an external Border Gateway Protocol (eBGP) route to
that of a locally sourced BGP route, causing it to be less preferred than an Interior Gateway Protocol (IGP)
route.
BGP Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.2.x
14
Implementing BGP