default gateway - interface name or IP...

Unanswered Question
Jan 14th, 2010

hi all,

just had an issue where routing stopped working and after changing the next hop on the default gateway from the interface name to the actual IP fixed the issue.

Before it was like this:

ip route 10.0.10.0 255.255.255.0 FastEthernet0/0

Then changed it to this and fixed the issue:

ip route 10.0.10.0 255.255.255.0 10.0.107.1

I remember reading somewhere that there is a difference but don't remember exactly what it is.

I have this problem too.
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Reza Sharifi Thu, 01/14/2010 - 06:26

Hello opers13,

The difference is that the admin distance for connected interface is 0 and for static route is 1.  The lower admin is more preferd over higher

HTH

Reza

Jon Marshall Thu, 01/14/2010 - 06:53

sharifimr wrote:

Hello opers13,

The difference is that the admin distance for connected interface is 0 and for static route is 1.  The lower admin is more preferd over higher

HTH

Reza

Reza

Just for your info.

This comes up now and then in these forums. Even though many books/articles make the same statement that AD is 1 for static to next-hop and 0 for static to interface in actual fact any static route has an AD of 1. So both the above routes will have AD 1. A long time ago apparently static routes to interface did have an AD of 0 but that has changed now. See this article  -

Static routes AD

Jon

Reza Sharifi Thu, 01/14/2010 - 07:24

Jon,

Thanks for the info and posting the paper.

You know, it is funny because I had read the same article a while back but I could not remember the fact that this has changed (I guess it is the age ha).

Reza

Giuseppe Larosa Thu, 01/14/2010 - 11:21

Hello Reza, Jon

I still think that the biggest difference is proxy ARP in the case of original poster between the two forms of static routing.

I agree that once there was a difference in AD value if using an ip next-hop or the interface name.

Or other device configuration has changed  (proxy ARP was disabled) or the ARP table of the router was somewhat full.

Hope to help

Giuseppe

Jon Marshall Thu, 01/14/2010 - 11:23

giuslar wrote:

Hello Reza, Jon

I still think that the biggest difference is proxy ARP in the case of original poster between the two forms of static routing.

I agree that once there was a difference in AD value if using an ip next-hop or the interface name.

Or other device configuration has changed  (proxy ARP was disabled) or the ARP table of the router was somewhat full.

Hope to help

Giuseppe

Giuseppe

I still think that the biggest difference is proxy ARP in the case of original poster between the two forms of static routing.

I agree. I don't think the AD had any effect on the original posters problem and if i suggested it did that wasn't my intention. I just wanted to share some info with Reza.

Jon

Giuseppe Larosa Thu, 01/14/2010 - 06:58

Hello Opers13,

when using an outgoing interface the local device relies on proxy-arp on other boxes.

That is the willingness of other devices to answer with their MAC address for ARP requests out of context for IP addresses that are not in the local subnet.

when using an IP next-hop it works even if the gateway/router has no ip proxy-arp.

This makes the difference.

To be noted that using the IP address next-hop is to be preferred to minimize ARP activity: only one ARP request is enough to resolve default gatewaty with proxy ARP a different request for each destination address is done

AD should be a secondary aspect here.

Hope to help

Giuseppe

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