From: Jay Hennigan (jay@west.net)
Date: Mon Feb 03 2003 - 15:18:50 GMT-3
On Mon, 3 Feb 2003, Luis Miguel Gil wrote:
> Hi, future ccies,
> I don't really understand the effect of the command "(no) peer neighbor
> route" when establishing a dialup connection between two routers. With the
> "no..." the routing does not install a connected route (/32) to the
> neighbor, but it install a proper route (i.e. a /24) to the same network.
> Without, wich is the default option, both (/32 and /24) appear in the
> routing table. So what ? I mean, what is the impact of having this route
> (/32) ? Everything works in the same way, I think...
The host route is installed as part of IPCP under PPP encapsulation.
The local interface's IP and netmask which should include the /32 host
address of the connected neighbor is present as connected whenever the
interface is up, so the peer neighbor route isn't really needed for
routing decisions on point-to-point links.
When applying a dynamic routing protocol to a network that includes the
PPP interface, the host route injected by PPP will be considered for
inclusion in the dynamic protocol as well as that of the local interface.
This can cause problems with demand circuits propagating the change of
state when the host route goes away after timeout, especially if there
is redistribution. By applying "no peer neighbor-route" to the interface,
you can suppress the PPP-injected host route. You can also use route maps
to filter it.
In production networks where some links are PPP and others HDLC, I like
to use the "no peer neighbor-route" on the PPP interfaces as it makes
the routing table cleaner not propagating host routes that are included
in the connected interface routes.
-- Jay Hennigan - CCIE #7880 - Network Administration - jay@west.net NetLojix Communications, Inc. - http://www.netlojix.com/ WestNet: Connecting you to the planet. 805 884-6323 .
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