OSPF & ISDN Backup Problems

Discussion in 'Cisco' started by NetWorkMan, Oct 15, 2007.

  1. NetWorkMan

    NetWorkMan Guest

    Hi Guys,

    I'm re-posting again, but this time I will explain my network better.

    We have recently switched over to MPLS. Previously we were running
    EIGRP and ISDN was working fine. We have 30 remote routers and 2
    central routers located in two different locations. So, it's a full
    mesh network however, we only serve business applications from the two
    central sites. The problem I'm having is when a branch fails over to
    ISDN the entire network slows down for a few seconds. I get a couple
    of time-outs on all of the routers. At the two central sites, we have
    PRI circuits for the remote sites to dial into when the primary links
    fail. All remote routers are set up as ABR routers. Serial
    interfaces are in area 0 and fastethernet interfaces are in different
    areas. (each site has different area). The ISDN interfaces at the
    remote routers are in area 0 and the dialer interfaces at the central
    sites are also in area 0. Should I place all ISDN interfaces in a
    separate area ? I tired placing the ISDN interfaces in a separate
    area, but then I was not able to route to the remote branch (had to
    reload the router). When a remote branch fails to ISDN I could see
    the neighbor relationship form. (successfully forms and it's in full
    loading stage, so no problems there). I could do static routes back
    to the remote routers, but I would like to have this set up
    dynamically if possible. Any input or suggestions would be greatly
    appreciated . Also, all remote routers are using floating static
    routes to activate the ISDN backup. I can post any router outputs if
    that helps.

    Thank you!
     
    NetWorkMan, Oct 15, 2007
    #1
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  2. NetWorkMan

    Trendkill Guest

    On Oct 15, 12:03 am, NetWorkMan <> wrote:
    > Hi Guys,
    >
    > I'm re-posting again, but this time I will explain my network better.
    >
    > We have recently switched over to MPLS. Previously we were running
    > EIGRP and ISDN was working fine. We have 30 remote routers and 2
    > central routers located in two different locations. So, it's a full
    > mesh network however, we only serve business applications from the two
    > central sites. The problem I'm having is when a branch fails over to
    > ISDN the entire network slows down for a few seconds. I get a couple
    > of time-outs on all of the routers. At the two central sites, we have
    > PRI circuits for the remote sites to dial into when the primary links
    > fail. All remote routers are set up as ABR routers. Serial
    > interfaces are in area 0 and fastethernet interfaces are in different
    > areas. (each site has different area). The ISDN interfaces at the
    > remote routers are in area 0 and the dialer interfaces at the central
    > sites are also in area 0. Should I place all ISDN interfaces in a
    > separate area ? I tired placing the ISDN interfaces in a separate
    > area, but then I was not able to route to the remote branch (had to
    > reload the router). When a remote branch fails to ISDN I could see
    > the neighbor relationship form. (successfully forms and it's in full
    > loading stage, so no problems there). I could do static routes back
    > to the remote routers, but I would like to have this set up
    > dynamically if possible. Any input or suggestions would be greatly
    > appreciated . Also, all remote routers are using floating static
    > routes to activate the ISDN backup. I can post any router outputs if
    > that helps.
    >
    > Thank you!


    While I have never run OSPF in a retail or branch situation, I would
    definitely advise you get those out of Area 0. When a link in area 0
    goes down, all of area 0 must reconverge and recalculate paths. For
    this reason, your entire network will come to crawl. When I worked
    for a very large grocery retailer (1,200 plus locations), we ran eigrp
    to the majority of the sites, although I think in your situation, stub
    areas might do you well. Regardless, try to avoid placing wan links
    in area 0, particularly those with any type of regular up/down
    behavior.
     
    Trendkill, Oct 15, 2007
    #2
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  3. NetWorkMan

    NetWorkMan Guest

    On Oct 15, 6:20 am, Trendkill <> wrote:
    > On Oct 15, 12:03 am, NetWorkMan <> wrote:
    >
    >
    >
    > > Hi Guys,

    >
    > > I'm re-posting again, but this time I will explain my network better.

    >
    > > We have recently switched over to MPLS. Previously we were running
    > > EIGRP and ISDN was working fine. We have 30 remote routers and 2
    > > central routers located in two different locations. So, it's a full
    > > mesh network however, we only serve business applications from the two
    > > central sites. The problem I'm having is when a branch fails over to
    > > ISDN the entire network slows down for a few seconds. I get a couple
    > > of time-outs on all of the routers. At the two central sites, we have
    > > PRI circuits for the remote sites to dial into when the primary links
    > > fail. All remote routers are set up as ABR routers. Serial
    > > interfaces are in area 0 and fastethernet interfaces are in different
    > > areas. (each site has different area). The ISDN interfaces at the
    > > remote routers are in area 0 and the dialer interfaces at the central
    > > sites are also in area 0. Should I place all ISDN interfaces in a
    > > separate area ? I tired placing the ISDN interfaces in a separate
    > > area, but then I was not able to route to the remote branch (had to
    > > reload the router). When a remote branch fails to ISDN I could see
    > > the neighbor relationship form. (successfully forms and it's in full
    > > loading stage, so no problems there). I could do static routes back
    > > to the remote routers, but I would like to have this set up
    > > dynamically if possible. Any input or suggestions would be greatly
    > > appreciated . Also, all remote routers are using floating static
    > > routes to activate the ISDN backup. I can post any router outputs if
    > > that helps.

    >
    > > Thank you!

    >
    > While I have never run OSPF in a retail or branch situation, I would
    > definitely advise you get those out of Area 0. When a link in area 0
    > goes down, all of area 0 must reconverge and recalculate paths. For
    > this reason, your entire network will come to crawl. When I worked
    > for a very large grocery retailer (1,200 plus locations), we ran eigrp
    > to the majority of the sites, although I think in your situation, stub
    > areas might do you well. Regardless, try to avoid placing wan links
    > in area 0, particularly those with any type of regular up/down
    > behavior.


    Our vendor only support OSPF and therefore we had to get rid of EIGRP.
    I may have to look into stub areas.
     
    NetWorkMan, Oct 15, 2007
    #3
  4. NetWorkMan wrote:
    > On Oct 15, 6:20 am, Trendkill <> wrote:
    >> On Oct 15, 12:03 am, NetWorkMan <> wrote:


    >> While I have never run OSPF in a retail or branch situation, I would
    >> definitely advise you get those out of Area 0. When a link in area 0
    >> goes down, all of area 0 must reconverge and recalculate paths. For
    >> this reason, your entire network will come to crawl. When I worked
    >> for a very large grocery retailer (1,200 plus locations), we ran eigrp
    >> to the majority of the sites, although I think in your situation, stub
    >> areas might do you well. Regardless, try to avoid placing wan links
    >> in area 0, particularly those with any type of regular up/down
    >> behavior.

    >
    > Our vendor only support OSPF and therefore we had to get rid of EIGRP.
    > I may have to look into stub areas.


    You can also move all ISDN links into different OSPF process.

    Regards,
    Andrey.
     
    Andrey Tarasov, Oct 15, 2007
    #4
  5. NetWorkMan

    stephen Guest

    "NetWorkMan" <> wrote in message
    news:...
    > Hi Guys,
    >
    > I'm re-posting again, but this time I will explain my network better.
    >
    > We have recently switched over to MPLS. Previously we were running
    > EIGRP and ISDN was working fine. We have 30 remote routers and 2
    > central routers located in two different locations. So, it's a full
    > mesh network however, we only serve business applications from the two
    > central sites. The problem I'm having is when a branch fails over to
    > ISDN the entire network slows down for a few seconds. I get a couple
    > of time-outs on all of the routers. At the two central sites, we have
    > PRI circuits for the remote sites to dial into when the primary links
    > fail. All remote routers are set up as ABR routers. Serial
    > interfaces are in area 0 and fastethernet interfaces are in different
    > areas. (each site has different area).


    Golden rule of OSPF - backbone should not be partitioned, even under fault
    conditions if you can avoid it.

    if there anything on the LAN at the remote sites?
    if not then putting them into a different area is not helping with scale,
    just making life more complicated.

    you can allow any other area to split into 2 bits and things will continue
    to work, but splitting area 0 causes black hole routing problems.

    The ISDN interfaces at the
    > remote routers are in area 0 and the dialer interfaces at the central
    > sites are also in area 0. Should I place all ISDN interfaces in a
    > separate area ? I tired placing the ISDN interfaces in a separate
    > area, but then I was not able to route to the remote branch (had to
    > reload the router).


    you would need a virtual link to make this work - note, not a good idea.

    usually a carrier MPLS cloud uses statics or BGP - do you actually have OSPF
    on the MPLS, or are you tunnelling with something like GRE?

    if the carrier is providing CE routers and you have OSPF neighbourship to
    them, then even though you are "talking" to them with OSPF there may not be
    native OSPF all the way through the cloud - in other words it isnt a single
    OSPF network.

    Or if it is some sort of Ethernet transport, maybe all layer 2, maybe the
    hits are actually spanning tree events?

    Sounds like you need a sniffer and deliberately cause some hits to see what
    is happening in detail.

    try putting "log-adj detail" in the OSPF config, and see what gets logged.

    When a remote branch fails to ISDN I could see
    > the neighbor relationship form. (successfully forms and it's in full
    > loading stage, so no problems there). I could do static routes back
    > to the remote routers, but I would like to have this set up
    > dynamically if possible. Any input or suggestions would be greatly
    > appreciated . Also, all remote routers are using floating static
    > routes to activate the ISDN backup. I can post any router outputs if
    > that helps.


    if you have floating statics anyway, then you dont really need OSPF on the
    backups -

    30+ routers is not big for OSPF - but the "mesh" you mentioned worrys me.

    log of events should help....
    >
    > Thank you!
    >

    --
    Regards

    - replace xyz with ntl
     
    stephen, Oct 15, 2007
    #5
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