14.3.6 Checking routes before filtering advertised routes
In basic terms, the routes subject to advertisement are the prioritized routes contained in the routing table. You can check which routes are subject to advertised route filtering by displaying the routes in the routing table.
To display the prioritized routes in the routing table, execute the show ip route operation command.
> show ip route Date 20XX/07/14 12:00:00 UTC Total: 8 routes Destination Next Hop Interface Metric Protocol Age 127/8 ---- localhost 0/0 Connected 1h 32s 127.0.0.1/32 127.0.0.1 localhost 0/0 Connected 1h 32s 172.10.1/24 192.168.1.145 VLAN0007 2/0 RIP 12s 192.168.1/24 192.168.1.1 VLAN0007 0/0 Connected 2s 192.168.1.1/32 192.168.1.1 VLAN0007 0/0 Connected 1h 31s 200.1/24 192.168.1.145 VLAN0007 -/- BGP 11m 26s 201.110/24 192.168.1.145 VLAN0007 1/1 OSPF ext2 52s 200.200.1/24 192.168.1.145 VLAN0007 0/0 Static 46m 58s |
To limit the command output to prioritized routes learned by a specific protocol, execute the show ip route operation command with the protocol specified as a parameter.
> show ip route rip Date 20XX/07/14 12:00:00 UTC Total: 5 routes Destination Next Hop Interface Metric Protocol Age 172.10.1/24 192.168.1.145 VLAN0007 2/0 RIP 12s |
To check detailed attribute information for the prioritized routes in the routing table, execute the show ip route operation command with the -F parameter specified.
> show ip route -F Date 20XX/07/14 12:00:00 UTC Total: 8 routes Destination Next Hop Interface Metric Protocol Age 127/8 ---- localhost 0/0 Connected 1h 46m, Distance: 0/0/0, Tag: 0, AS-Path: IGP (Id 1), Communities: -, LocalPref: -, <NoAdvise Active Retain Reject> 127.0.0.1/32 127.0.0.1 localhost 0/0 Connected 1h 46m, Distance: 0/0/0, Tag: 0, AS-Path: IGP (Id 1), Communities: -, LocalPref: -, <NoAdvise Active Retain> 172.10.1/24 192.168.1.145 VLAN0007 2/0 RIP 19s, Distance: 120/0/0, Tag: 0, AS-Path: IGP (Id 1), Communities: -, LocalPref: -,<Int Active Gateway> 192.168.1/24 192.168.1.1 VLAN0007 0/0 Connected 7s, Distance: 0/0/0, Tag: 0, AS-Path: IGP (Id 1), Communities: -, LocalPref: -, <Active Retain> 177.7.7.1/32 192.168.1.1 VLAN0007 0/0 Connected 1h 45m, Distance: 0/0/0, Tag: 0, AS-Path: IGP (Id 1), Communities: -, LocalPref: -, <NoAdvise Active Retain> 200.1/24 192.168.1.145 VLAN0007 -/- BGP 12m 57s, Distance: 20/0/0, Tag: 0, AS-Path: 1000 IGP (Id 3), Communities: 120:200, LocalPref: 100, <Ext Active Gateway> 201.110.1/24 192.168.1.145 VLAN0007 1/1 OSPF ext2 3m 34s, Distance: 110/1/0, Tag: 10, AS-Path: IGP (Id 1), Communities: -, LocalPref: -, <Int Ext Active Gateway> 200.200.1/24 192.168.1.145 VLAN0007 0/0 Static 1h 0m, Distance: 2/0/0, Tag: 0, AS-Path: IGP (Id 1), Communities: -, LocalPref: -, <Remote Int Active Gateway> |
The BGP4 protocol sometimes advertises routes that do not have priority in the routing table. To include non-priority BGP4 routes in the output of the show ip route operation command, execute the command with the all-routes and bgp parameters specified.
> show ip route all-routes bgp
Date 20XX/07/14 12:00:00 UTC
Status Codes: * valid, > active, r RIB failure
Total: 12 routes
Destination Next Hop Interface Metric Protocol Age
*> 200.1/24 192.168.1.145 VLAN0007 -/- BGP 11m 26s-
* 200.200.1/24 192.168.1.145 VLAN0007 -/- BGP 50m 14s-
# |
- #
-
The characters * and > at the beginning of an entry signify the following:
*: Signifies a valid route. Its absence indicates an invalid route.
>: Signifies a prioritized route. Only prioritized routes are used for packet transfer.