Configuring two T1 lines in cisco 2600 (Total 4 Mbps) from two diffferent providers

Discussion in 'Cisco' started by Kothanns, Nov 5, 2005.

  1. Kothanns

    Kothanns Guest

    We h've Cisco 2600 for which we presently use one 2 Mbps T1 link. For
    upgradtion we brought a additional 2 Mbps T1 link from a diffrent
    provider. Can these two T1 lines be brought to 4 Mbps so that the total
    traffics would serve around 3000 users for internet.

    Req to provide assitance asap.
    Kothanns, Nov 5, 2005
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  2. Kothanns

    uberhaxor Guest

    There are QoS techniques such as MLPPP that can bundle multiple
    physical links into one logical link, but only when connected to the
    same provider. Load balancing is not an option either for the same
    reason. What you can do is Multihomed Load Sharing to the different
    providers by using route maps. The first route map will permit public
    IP addresses up on the first serial interface. The second
    route map will permit public IP addresses above on the second
    serial interface. Below is a example of what a Multihomed Load Sharing
    configuration with two T-1s (1.5Mbps) should look like.

    Good Luck

    interface Serial 0/0
    Description T1 TO PROVIDER-1
    ip address
    no ip route-cache

    interface Serial 0/1
    Description T1 TO PROVIDER-2
    ip address
    no ip route-cache

    router bgp 300
    neighbor remote-as 111
    neighbor route-map PROVIDER-1 in
    neighbor remote-as 222
    neighbor route-map PROVIDER-2 in

    route-map PROVIDER-1 permit 10
    match ip address 1
    set weight 100

    route-map PROVIDER-1 permit 20
    match ip address 2

    route-map PROVIDER-2 permit 10
    match ip address 1

    route-map PROVIDER-2 permit 20
    match ip address 2
    set weight 100

    access-list 1 permit
    access-list 2 deny
    access-list 2 permit any
    uberhaxor, Nov 5, 2005
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  3. Kothanns

    Matty M Guest

    Ahh but wont the other ISP have to talk BGP to his router?


    Matty M, Nov 5, 2005
  4. Kothanns

    anybody43 Guest

    We h've Cisco 2600 for which we presently use one 2 Mbps T1 link. For
    The usual way to do this if you don't have you own
    IP address allocation is to use policy based routing
    to route certain traffic out of one port
    or other, and other traffic out of the other port.

    You then NAT on the external interfaces.

    Since the traffic is NATted differently for each port,
    the return traffic gets correctly routed.

    Clearly this "statically configured" load balancing is
    unlikely to produce optimal load balancing however
    it may be what you want.

    The following will allow you to achieve resilience with PBR.
    Way cool and groovy.

    Just add NAT stir and bake for 40 mins.
    anybody43, Nov 6, 2005
  5. Just be prepared for egg on your face and have your resume ready...

    PBR Support for Multiple Tracking Options appears to only be
    supported in Enterprise feature sets. So first you will need to
    upgrade your router (at considerable cost, last time I checked,
    but that depends upon the platform and assumes your platform is
    hefty enough to support it. Flash and/or RAM upgrades may also
    be required).

    Once you upgrade it, you will discover using NAT with PBR requires
    use of policy based NAT, which also works, but uncovers a nasty
    side effect of Cisco's policy based NAT implementation. Policy
    based NAT is only used to determine a NAT if there is no NAT for
    that flow already in the NAT connection table. Once a NAT entry is
    in the table, it will always be used regardless of the actual path
    taken by the packet. A connection stays in the table until either
    it times out or an interface defining its address fails.

    Way cool and groovy combination of features, except it doesn't
    work because of the details of how the individual features are
    implemented. On the other hand, if you can set it up so that the
    router doing the policy based routing does not need to NAT on both
    outside links, then you truly are way cool and groovy.

    Been there, done that, been burnt... fortunately the cooking was
    done in the lab before committing to production, so the damage was
    minimal. But a classic example of "In theory, there is no difference
    between theory and practice. In practice, there is."

    Good luck and have fun!
    Vincent C Jones, Nov 7, 2005
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