Dynamic Route or Default Route

Unanswered Question
Jul 23rd, 2008

When both routes are configured on the router,which route will take precedence to route traffic to the destination.

I have this problem too.
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srue Thu, 07/24/2008 - 01:41

the most specific route, which is usually the dynamically learned route. you can have default routes injected via dynamic routing btw.

lamav Fri, 07/25/2008 - 08:05

I think you are asking which default route would be placed in the routing table in the event that one is learned dynamically and the other statically.

For example, one learned from OSPF and the other statically.

Something like that?

If so, the static route will be used because it has a lower Administrative Distance (AD) than any dynamic route, by default.

When comparable routes (same prefix length - specificity) are received by a router from the same routing protocol, it will select the one with the best metric and place it in the routing table. If, however, they come from 2 different sources, the AD will be examined and the one with the lower AD will be placed in the routing table.

Lastly, if the 2 routes are not comparable (different prefix lengths), it will utilize the more specific route to the destination, although both may exist in the routing table.

HTH

Victor

AJAZ NAWAZ Fri, 07/25/2008 - 08:18

A static default would win over a dynamic default route.

That said, a static default pointing to an interface would be preferred over a static default pointing to a next-hop ip address.

test it you will see :-)

hth,

Ajaz

AJAZ NAWAZ Mon, 07/28/2008 - 22:31

Yes and the router uses the AD to select the 'Best' default.

One point to note here is that the best default available on a router is zero (0), and it looks like this:

ip route 0.0.0.0 0.0.0.0 gigabit 1/0

And to complete the picture the following route will have the next best default on offer and as you can see points to an IP next-hop:

ip route 0.0.0.0 0.0.0.0 192.168.1.254

If there is no static route, and two defaults are being received by dynamic routing protocols, the one with the best AD will make it into the routing table. An eBGP default is the next best and so on and so forth (i.e. eigrp, ospf..)

hth,

Ajaz

lamav Tue, 07/29/2008 - 04:13

Kalyan:

Why don't you read what I wrote to you?

I answered that question.

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