static routing.....

Unanswered Question
May 25th, 2009
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very simple & very very silly question....


what's the logic in having a static route up if you have not valid adj?

I mean static routes are up even if i have no a valid L2 next-hop available (physical link up but logical down on other side, due to misconfiguration or stuff like that i don't know)....why for eth. and static routing there's not some mechanism for putting down a route (maybe after some time) if i haven't got a right L2 adj?

of course without using bfd, ip sla or stuff like that...


thx


Das

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SJessulat_2 Mon, 05/25/2009 - 21:28
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Hi Das,


if you're talking about a network, where every destination can be reached through redundant L3-Links, then you're right.


But let's assume, there is a L2-Subnet, which can only be reached through one L3-device. Or you have a stub router, which only needs one route to reach every other destination. In this case, a static route would be appropriate. It wouldn't help to bring the route down in case of link-failure, because there is no other way to this subnet.


Hth,


Sebastian

danilodicesare Mon, 05/25/2009 - 21:55
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Hi Sebastian,


yes of course....but just figure a topology like this:


MLS1(VLAN10) -->A_MLS2(VLAN10)-->something

-->B_L3(Dot1Q10)-->something

-->C_MLS4(VLAN10)-->something


and some redundant route pointing towards from MLS1 trought A-B-C for reaching 'something'....and maybe having CEF(trie)/adj stuff....why having 'valid' route and not a valid adj and loosing packet?

I may add keyword permanent if i want a useless route for any reason. could be useful in ethernet env, maybe not for other media type/tecnology.


thx


Das

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