PBR question

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Oct 27th, 2007

Hi All

My question is that if The command "set ip defualt next-hop X" and "ip route 0.0.0.0 0.0.0.0 X" is some effect ?

thank you .

I have this problem too.
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JORGE RODRIGUEZ Sat, 10/27/2007 - 08:01

Hi,

it appears the word "default gets confused with default route , both commands have different effects and usage, "set ip default next-hop " in PBR does not by any means defines a default route, however, if next hop IP router have a default route or gateway of last resort the router you are applying the PBR will forward the traffic to that router who has "IP route 0.0.0.0 0.0.0.0 x.x.x.x " command or gateway of last resort .

Using IP route 0.0.0.0 0.0.0.0 x simply defines gateway of last resort on a router.

you may configure set ip default next-hop x.x.x.x with a defualt route through the ACL of PBR.

Here are couple of PBR basic examples that can clarify much more your question.

http://www.cisco.com/en/US/tech/tk364/technologies_configuration_example09186a00801f3b54.shtml#intro

HTH

Jorge

jj-zhou Sat, 10/27/2007 - 17:42

Hi Jorge

I have read the doc, can I understand if both "ip route 0.0.0.0 0.0.0.0 A" and "set ip default next-hop B or A" without match are configured on router ,the "set ip default" without match is more priority ?

bvsnarayana03 Sat, 10/27/2007 - 08:56

"Set ip default next-hop x.x.x.x", defines next-hop for those packets which matches the condition in the "match" command of the PBR.

While "ip route 0.0.0.0 0.0.0.0 x.x.x.x", defines the next hop for those pkts which doent match the PBR.

ilya.varlashkin Sat, 10/27/2007 - 09:02

'ip route 0.0.0.0 0.0.0.0' is like applying unconditional (no 'match') PBR to all interfaces, but such use of PBR is rare and hardly justified.

If a packet didn't match any of the blocks of your PBR route-map then it falls back to normal routing lookup. Whether it will use default route or not, depends on your routing table.

On the other hand, if packet matches your match statements and there is specific route in the routing table, which would have been used otherwise then you need 'set ip next-hop X' (notice, no 'default'). If route-map matches, but there is no explicit route to the destination, then you should use 'set ip default next-hop'.

/iLya

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