intervlan routing and policy routing C3750 or C 4948

Discussion in 'Cisco' started by [email protected], Oct 19, 2005.

  1. Hi,

    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
    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

    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

    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


    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

    [email protected], Oct 19, 2005
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  2. You may tray to play with ip vrf.
    Tomasz Paszkowski, Oct 20, 2005
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  3. Sied@r

    anybody43 Guest

    I tried to run policy routing on incoming vlan

    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.
    anybody43, Oct 20, 2005
  4. Tomasz Paszkowski napisa³(a):
    How it works ? Are you use it ?
    [email protected], Oct 20, 2005
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