intervlan routing and policy routing C3750 or C 4948


I'm testing before I buy it cisco 3750G.(i'm thinking about 4948 to )

I want use this switch as L3 router for my network.

I want to keep intervlan routing on the switch (about 50 vlans with L3 routing) and for some vlans i need different gateways.

I tried to run policy routing on incoming vlan

interface Vlan10 ip address ip policy route-map test

interface Vlan11 ip address

interface Vlan100 ip address

access-list 1300 permit route-map test permit 1300 match ip address 1300 set ip next-hop

in this scenerio all packets from vlan 10 are policy routed to even traffic to vlan11.

I want policy routing for packets that aren't in local routing table.

I found on newsgroups " If you use "set ip next-hop" or "set interface," the precedence is: 1) route-map, 2) routing table. So if the interface specified in the route-map is up, or if the next-hop specified in the route-map appears in the routing table, then the packets will be routed according to the route-map set statement. If, on the other hand the next-hop is not in the routing table/interface is down, then the policy will be ignored and the packet will be routed according to the routing table (standard IOS routing). If you instead use "set ip default next-hop" or "set default interface," the behavior is exact opposite. In this case, the precedence is: 1) routing table, 2) route-map. So if the destination matches anything in the routing table (including a default route), the route-map will never be used. If there is no match in the routing table for the dest IP, then the route-map will be used to forward the packet (assuming the specified next-hop appears in the routing table/specified interface is up). "

but set ip default next-hop isn't CEF or Fastswitching operation for

3750G or 4948

for C 4500 ( I Think it will applay to 4948 - which is based on C4500) I found this:

The Catalyst 4500 switching engine supports matching a "set next-hop" route-map action with a packet on a permit ACL. All other route-map actions, as well as matches of deny ACLs, are supported by a flow switching model. In this model, the first packet on a flow that matches a route-map will be delivered to the software for forwarding. Software determines the correct destination for the packet and installs an entry into the TCAM so that future packets on that flow are switched in hardware. The Catalyst 4500 switching engine supports a maximum of 4096 flows

for C 3750 I found this:

IP PBR can now be fast-switched. Prior to Cisco IOS Release 12.0, PBR could only be process-switched, which meant that on most platforms the switching rate was approximately 1000 to 10,000 packets per second. This speed was not fast enough for many applications. Users who need PBR to occur at faster speeds can now implement PBR without slowing down the router.

Fast-switched PBR supports all of the match commands and most of the set commands, with the following restrictions:

  • The set ip default next-hop and set default interface commands are not supported. * The set interface command is supported only over point-to-point links, unless a route-cache entry exists using the same interface specified in the set interface command in the route map. Also, at the process level, the routing table is consulted to determine if the interface is on a reasonable path to the destination. During fast switching, the software does not make this check. Instead, if the packet matches, the software blindly forwards the packet to the specified interface.


There is posibility to use intervlan routing and pbr for vlans to route outside local routing table via separate gateways (no default gateway) and do it in hardware ?

Switch C3750G or C4948.

Thanks a lot for any good informations


Reply to
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W artykule Sied@r napisa³(a):

You may tray to play with ip vrf.

Reply to
Tomasz Paszkowski

I may be old fashioned however policy routing is in my view a band aid. I would be reluctant to consider it for a new design. Make that /very/ reluctant. If someone is telling you that they must have the facility provided by it why not save a lot of trouble and get that new job now:-)

- The 4500 sounds reasonably promising.

It is not clear from this if they are talking about hardware or software based switching. This is deliberate on Cisco's part in the hope that you will buy it anyway. Fastswitching is DEFINATELY software so it would seem that in this case CEF is software which is unlikely to be any use to you.

Neither fast /nor/ process switching use hardware based IP routing. The performance will be terrible.

Avoid PBR - Just don't do it.

If you /must/ do it get your supplier to state in writing that the forwarding rate for PBR is xxxMpps where xxx is whatever is in the brochure for your chosen model. Get ready to sue.

Finally I suspect that you will find that not many beta testers -oops- ^h^h... customers use PBR and so you will need to be on the look out for gremlins.

/* Rant off */

Have fun. - Sorry Vincent but I like that too.

Reply to

Tomasz Paszkowski napisa=B3(a):

How it works ? Are you use it ?

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