Re: PBR on 1841 (no NAT, no ACLs, dual ADSL)

Discussion in 'Cisco' started by bod43, Dec 7, 2010.

  1. bod43

    bod43 Guest

    On Dec 6, 8:52 am, Martin Johnson <> wrote:
    > On 05/12/2010 20:11, Martin Johnson wrote:
    >
    >
    >
    > > On 04/12/2010 23:43, Martin Johnson wrote:

    >
    > >> I'd just like to do some crude QoS for VOIP egress traffic. That is,
    > >> when both ADSL lines are up, I'd like to force the VOIP egress traffic
    > >> up one line, and force all other egress traffic up the other line.  This
    > >> should preserve VOIP call quality when I'm uploading files to the
    > >> Internet.  Also it would avoid the possibility of out-of-order VOIP
    > >> packet delivery due to asymmetrical routing.  The ISP already does QoS
    > >> for VOIP on the downlink side, so protecting VOIP uplink traffic is the
    > >> missing piece of the puzzle for me.

    >
    > >>        access-list 110 permit ip   host 81.187.151.42 any
    > >>        access-list 110 permit icmp host 81.187.151.42 any

    >
    > >>        route-map voip permit 10
    > >>                match ip address 110
    > >>                set interface dialer0

    >
    > >>        route-map voip permit 20
    > >>                set interface dialer1

    >
    > >>        interface fa0/0
    > >>                ip policy route-map voip

    >
    > > As noted earlier, this worked OK after I turned fast switching off and
    > > on again. Before that, incoming requests to my servers were dropped.

    >
    > > The only continuing drawback with this configuration is that when one
    > > ADSL line fails, the egress traffic doesn't fail over to the surviving
    > > line.   I tried switching off both fast switching and CEF, to no effect.

    >
    > > Is there a way of achieving fall-back routing with a route-map ?

    >
    > > I do have default routes, but they don't seem to fix this!

    >
    > >    ip route 0.0.0.0 0.0.0.0 Dialer0
    > >    ip route 0.0.0.0 0.0.0.0 Dialer1

    >
    > > Is it worth updating from IOS 12.4 to 15.1 to see if that's any better?

    >
    > Latest suggestion to get the fallback routing working, is to combine IP
    > SLA and VRF.  May need VOIP server to be moved to the spare Ethernet
    > interface.  I'll post a working config if I get it working.


    1.
    the no ip route-c, ip route-c was (obviously)
    not suopposed to fix anything:)

    Have a look to see that the interface config is the same as
    you had originally. Please post result of sh run int
    FastEthernet0/0. Maybe you have indeed turned off CEF
    or somehting.

    2. Depending on the failures you want to protect against
    there are various fallback options.

    SLA is the most robust since you can detect failure
    anywhere in the path.

    If you though are content to detect only failures that
    cause the dialer to go down then you should be
    able to use PBR with normal routing as a fallback.
    By default if the specified PBR interface is not available then
    it automatically falls back to normal routing.

    I am not sure why you might need VRFs. I am quite likely
    missinformed:)

    Finally unless the config was changed by the route-cache
    stuff you must have run into a bug OR have changed
    something else in your network inadvertently OR
    of course your ISP changes something.
     
    bod43, Dec 7, 2010
    #1
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