Poor man's bandwidth management - floating static question

Discussion in 'Cisco' started by Patrick M. Hausen, Jul 9, 2008.

  1. Hello,

    for a particular installation I have set up two internet
    connections - one via leased line with fixed static IP addresses,
    the other one with PPPoE and dynamic IP addresses.

    The latter is a typical consumer product, i.e. "dirt cheap",
    high bandwidth downstream and billed flat. The leased line
    is a "business product" and offers less bandwidth, but
    symmetrical and with lower RTTs and better SLAs.

    The customer intends to use the cheap line for HTTP downloads
    as long as it is available. This was not that difficult to set
    up via policy routing:

    1. the leased line:
    interface FastEthernet1
    description leased line uplink
    ip address x.y.z.42

    ip route x.y.z.41 250

    interface Vlan3
    description static network assigned by provider
    ip address x.y.z.57
    ip nat inside
    ip route-cache policy
    ip policy route-map no-http

    See below for the NAT and policy config.

    2. The cheap line:
    interface FastEthernet0
    description TDSL-Flat
    no ip address
    pppoe-client dial-pool-number 1

    interface Dialer1
    description TDSL-Flat 1
    ip address negotiated
    ip mtu 1448
    ip nat outside
    ip virtual-reassembly
    encapsulation ppp
    dialer pool 1
    dialer idle-timeout 0
    dialer enable-timeout 2
    dialer persistent
    dialer-group 1
    ... (deleted PPP auth parameters)

    ip route Dialer1
    dialer-list 1 protocol ip permit

    ip nat inside source list nat interface Dialer1 overload

    ip access-list extended nat
    permit ip x.y.z.56 any
    deny ip any any

    So we are NATing the official IP addresses assigned by the provider
    for the leased line for all traffic that is sent out the cheap one.

    3. The policy route-map
    ip access-list extended no-http
    deny tcp any any eq www
    permit ip any any

    route-map no-http permit 10
    match ip address no-http
    set ip next-hop x.y.z.41

    This sends anything but traffic destined to port 80 out the
    leased line and leaves traffic to port 80 alone, so it's
    send out the cheap line.

    The entire setup works as intended but for one minor point.
    In case the cheap PPPoE line fails, we want to use the
    leased line for HTTP traffic. I intended to do this
    via a floating static route, hence the two default route
    entries you see above.

    Unfortunately it seems not to work that way. If I administratively
    shutdown Dialer1, the result is as expected. The route to Dialer1
    is deleted from the routing table and the route to x.y.z.41 is

    But this is not the common mode of failure of that PPPoE line.
    If I simulate a failure on the cheap provider's side by
    administratively shutting down Fa0, the Dialer1 obviously
    times out and shuts down, eventually. Yet, the default
    route to Dialer1 is not deleted. The Dialer1 interface
    stays "up, line protocol is up (spoofing)", so the route
    stays in the routing table.

    Any hints on how to solve this greatly appreciated.

    Patrick M. Hausen, Jul 9, 2008
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  2. Hello,

    never mind, I found a solution:

    int di1
    description this is the cheap leased line that fortunately has got a fixed static IP address
    dialer persistent
    ! track the static IP
    track 1 ip route w.x.y.z reachability
    ip route Dialer1 track 1

    Kind regards,
    Patrick M. Hausen, Jul 9, 2008
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  3. Patrick M. Hausen

    Trendkill Guest

    PBR w/ tracking options. If your next hop on the PPoE is a public
    hop, you may need to block ping to that address out of the other
    router, but this should work if your feature set supports it:

    Trendkill, Jul 9, 2008
  4. Hello,

    Though this is not needed in my particular situation (see my other
    post), it looks really interesting. Thanks for the link.

    Kind regards,
    Patrick M. Hausen, Jul 9, 2008
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