Show ip bgp

To display entries in the BGP routing table, use the show ip bgp EXEC command. ■ show ip bgp [network] [network-mask] [longer-prefixes]

When details are displayed for a specific route entry in the BGP table, the next hop and AS path are displayed along with information that indicates whether a BGP update was received over an intra-confederation EBGP session or a regular EBGP session.

Syntax Description

Parameter

Description

network

Network number, which is entered to display a particular network in the BGP routing table

network-mask

Displays all BGP routes that match the address and mask pair

longer-prefixes

Displays the network route and its more specific routes

6-74 Configuring BGP on Cisco Routers (BGP) v3.2 © 2005, Cisco Systems, Inc.

In the figure, the show ip bgp neighbors command has been executed on a router within a confederation. As a result, information about the intra-confederation EBGP session is displayed. The session is an external link (indicating an EBGP session) under common administration (indicating an intra-confederation EBGP session).

© 2005, Cisco Systems, Inc. Scaling Service Provider Networks 6-75

Route Received from Intra-Confederation IBGP Session

Next hop points to real EBGP peer in both cases.

EBGP)

router! show ip bgp 14.0.0.0

BGP routing table entry for 14.0.0.0/8, version 5 Paths: (2 available, best #2, advertised over IBGP, (65001) 387

—► 1.3.0.3 (metric 543S7248) from 1.0.0.1 (11.0.0.1)

Origin IGP, metric 0, localpref 60, valid, confed-internal

Origin IGP, metric 0, localpref 60, valid, confed-external, best _

Intra-Confederation Part of AS Path

External Part of AS Path

Route Received from Inter-Confederation EBGP Session

In this example, the show ip bgp command is executed on a router within the confederation to display information about the class A network 14.0.0.0.

The command response indicates that the router has received information about the network 14.0.0.0 on two different BGP sessions. One of the sessions is an intra-confederation EBGP session, and the other session is an IBGP session. Both updates have the same next-hop address, which was set by the true EBGP peer that originally sent the update into the confederation. The next hop is resolved by recursive routing, and, therefore, the forwarding decision will be the same regardless of which BGP entries are actually used. The second IP address is the address of the neighbor, which is followed by the router-ID of that neighbor (enclosed in parentheses).

The AS path is the same for both entries. It contains a parenthesized number, (65001). This is the part of the AS path that describes the intra-confederation AS path. The part of the AS path that follows is the external part, 387. This number reveals that the confederation has a true EBGP session with the official AS (AS 387), from which an update about network 14.0.0.0 was received. The update was forwarded to the router using IBGP within member-AS 65001. The router in the local member-AS on which this command was executed has two different intra-confederation EBGP sessions with member-AS 65001. So, the update about network 14.0.0.0 has entered the local AS via two different paths.

6-76 Configuring BGP on Cisco Routers (BGP) v3.2 © 2005, Cisco Systems, Inc.

Was this article helpful?

0 0
Search Engine Optimization Overview

Search Engine Optimization Overview

This is the 2nd volume of a 9 volume series called the Webmasters Toolbox package. Search engines are the number one way that internet users find websites. In most cases, a listing in a search engine is free. So, it's no surprise that Search Engine Optimization SEO is often the first priority when marketing a website.

Get My Free Ebook


Post a comment