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static ip route

Hi Folks

in static route,what is the difference between the next hope represent an ip address and next hop represent a physical interface

thanks

6 REPLIES
Hall of Fame Super Bronze

Re: static ip route

http://www.cisco.com/en/US/docs/ios/iproute_pi/command/reference/iri_pi1.html#wp1037816

The usage guideline describes the differences in detail.

static ip route

Br.  Ibrahim

There is no difference as far as, route preference over a static-route pointing to a “physical interface name” compare to nexthop ip-address. 

Advantage is IP address on physical address could change administratively but it does not require to change the given static route pointing to that physical interface-name (i.e local interface name), as a “static route” always point to a physical interface name, which never change.

in DSL setup you always point (i.e. static-route), to your local dialer interface as you would never know, what is your next hop ip address.

I hope that answers your question.

thanks

Rizwan Rafeek

Purple

static ip route

Hi,

on multipoint interfaces always configure the next-hop or both if you want to save the recursive lookup.

on point-to-point you can configure the interface which will save you a recursive lookup.

Regards.

Alain

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Cisco Employee

Re: static ip route

Ibrahim

From routing perspective - there is no difference.

But please consider following:

If you use next-hop ip address - your router will have mac address of next hop in it's table. So after finding the next hop for a packet it will be switched towards next router using MAC address from the table.

When you use an outgoing interface in your static route - for all unknown destination ip addresses router will send ARP request which may cause big impact on a router cpu and bandwidth.

HTH,

Alex

Bronze

static ip route

The one thing I've noticed regarding a difference from a routing perspective is with NX-OS routing behavior.  Being this is in the WAN discussion - so may not be relevant - but it is something I have been burned by so hopefully this will help someone else!

When defining static routes in IOS with a next-hop address, and the L3 interface directly connected to that next-hop goes down - the static route is removed from the routing table.

If you define a static route in NX-OS with next-hop address, and the L3 interface directly connected to the static route goes down - the static route dynamically defines itself to the next most specific match - e.g. the default route.  This very well may not be the preferred outcome.  If you want it to behave like IOS and remove the static route from the routing table, you need to specify both the physical interface and the next-hop address.

Matt

Hall of Fame Super Gold

static ip route

Matt

That is a very helpful insight and I give you +5 for sharing this insight. I would certainly be surprised the first time that I encountered this behavior.

HTH

Rick

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