< Free Open Study >

Syntax Description:

• ip-address— Neighbor’s IP address.

• peer-group-name— Name of the peer group. See section 8-19.

• route-map-name— Name of the route map used to select routes to be unsuppressed.

Purpose: When the aggregate-address command is used with the summary-only option, the more-specific routes of the aggregate are suppressed (see section 1-7). The aggregate-address summary-only command suppresses the more-specific routes to all neighbors. You can use an unsuppress map to selectively leak more-specific routes to a particular neighbor.

Cisco IOS Software Release: 10.0. Peer group support was added in Release 11.0.

Configuration Example: Selectively Advertising Routes with an Unsuppress Map

In Figure 8-31, Router A is advertising four prefixes to Router B. Router B aggregates these prefixes and advertises only the summary while suppressing the four specific routes. This will be used as the initial configuration so that we can inspect the BGP tables for Routers B and C. The unsuppress map is then added to Router B’s configuration.

Figure 8-31. Globally Suppressed Routes Can Be Selectively Unsuppressed on a Per-Neighbor Basis

Router A

interface Loopback0

 ip address 172.16.0.1 255.255.255.0

!

interface Loopback1

 ip address 172.16.1.1 255.255.255.0

!

interface Loopback2

 ip address 172.16.2.1 255.255.255.0

!

interface Loopback3

 ip address 172.16.3.1 255.255.255.0

!

router bgp 65530

 network 172.16.0.0 mask 255.255.255.0

 network 172.16.1.0 mask 255.255.255.0

 network 172.16.2.0 mask 255.255.255.0

 network 172.16.3.0 mask 255.255.255.0

 neighbor 10.1.1.2 remote-as 1

__________________________________________________________________________

Router B

router bgp 1

 aggregate-address 172.16.0.0 255.255.0.0 summary-only

 neighbor 10.1.1.1 remote-as 65530

 neighbor 10.1.2.2 remote-as 2

__________________________________________________________________________

Router C

router bgp 2

 neighbor 10.1.2.1 remote-as 1

Before proceeding to the unsuppress map, check the BGP tables on Routers B and C:

rtrB#show ip bgp

BGP table version is 42, local router ID is 172.16.1.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete



   Network          Next Hop            Metric LocPrf Weight Path

s> 172.16.0.0/24    10.1.1.1                 0             0 65530 i

*> 172.16.0.0       0.0.0.0                            32768 i

s> 172.16.1.0/24    10.1.1.1                 0             0 65530 i

s> 172.16.2.0/24    10.1.1.1                 0             0 65530 i

s> 172.16.3.0/24    10.1.1.1                 0             0 65530 i

__________________________________________________________________________

rtrC#show ip bgp

BGP table version is 10, local router ID is 156.26.32.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete



   Network          Next Hop            Metric LocPrf Weight Path

*> 172.16.0.0       10.1.2.1                               0 1 i

As you can see, Router B is suppressing the more-specific routes. Next, we want to unsuppress prefix 172.16.2.0 on Router B and allow this route to be advertised to Router C:

Router B

router bgp 1

 aggregate-address 172.16.0.0 255.255.0.0 summary-only

 neighbor 10.1.1.1 remote-as 65530

 neighbor 10.1.2.2 remote-as 2

 neighbor 10.1.2.2 unsuppress-map allow

!

access-list 1 permit 172.16.2.0 0.0.0.255

route-map allow permit 10

 match ip address 1

Verification

There should be no change to Router B’s BGP table:

rtrB#sh ip bgp

BGP table version is 10, local router ID is 172.16.1.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete



   Network          Next Hop            Metric LocPrf Weight Path

s> 172.16.0.0/24    10.1.1.1                 0             0 65530 i

*> 172.16.0.0       0.0.0.0                            32768 i

s> 172.16.1.0/24    10.1.1.1                 0             0 65530 i

s> 172.16.2.0/24    10.1.1.1                 0             0 65530 i

s> 172.16.3.0/24    10.1.1.1                 0             0 65530 i

However, Router C should not be receiving the unsuppressed route:

RtrC#sh ip bgp

BGP table version is 14, local router ID is 156.26.32.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete



   Network          Next Hop            Metric LocPrf Weight Path

*> 172.16.0.0       10.1.2.1                               0 1 i

*> 172.16.2.0/24    10.1.2.1                               0 1 65530 i

Troubleshooting

1. Verify that the BGP neighbors are in the Established state using the show ip bgp neighbors command.

   If the neighbor relationship is not in the Established state, see section 8-23.

2. Check to see that the route you want to unsuppress is actually being suppressed by executing the show ip bgp command.

3. The route map should permit only routes that are to be unsuppressed. Check your syntax.

4. Check the syntax of your access list.

< Free Open Study >