Options

DMVPN Tunnels with EIGRP

RS_MCPRS_MCP Member Posts: 352
in CCNP
Hi All,

I have an DMVPN Router which has an Tunnel Interface configured to establish connections with various Routers internationally.

I am using NHRP & EIGRP to establish the connections and routes.

The problem I am having is that some of the Tunnel Interfaces on various routers keep flapping. They keep renewing themselves every 2-3 hours where as some of the connections dont and have been up for days and weeks.

Why is this flapping occuring? Why are the routes renewing themselves whilst other connections are not?

According to Cisco, certain IOS's on ISR's cause flapping, this requires an upgrade of the IOS to resolve, however I do not want to carry that out in an live environment, especially remotely.

Are there any other troubleshooting steps or solutions?

Thanks :)
· Share on FacebookShare on Twitter

Comments

  • Options
    keenonkeenon Member Posts: 1,922 ■■■■□□□□□□
    if its a known bug in the IOS version your using your choices are limited
    Become the stainless steel sharp knife in a drawer full of rusty spoons
    · Share on FacebookShare on Twitter
  • Options
    burbankmarcburbankmarc Member Posts: 460
    Do you happen to have the bug id for this? I have a 2811 that drops a tunnel every now and again and this might be the cause of it.
    · Share on FacebookShare on Twitter
  • Options
    ilcram19-2ilcram19-2 Banned Posts: 436
    what is the delay and MTU size setup on the tunnel interface spoke and hub?
    · Share on FacebookShare on Twitter
  • Options
    RS_MCPRS_MCP Member Posts: 352
    On the DMVPN Router (Delay is 500, MTU 1500) IOS: 12.4 (23) Cisco 7206VXR
    On the Spoke Router (No Delay Configured, MTU 1400) IOS: 12.4 (15) Cisco 1841

    Cisco Bug: https://supportforums.cisco.com/docs/DOC-4046;jsessionid=434591C7BEB1642F61D82339C260F650.node0

    Any futher information, then please let me know.
    · Share on FacebookShare on Twitter
  • Options
    CyanicCyanic Member Posts: 289
    That is a tough one. If you need to do an upgrade there has to be a method for you to schedule an outage as there should be some expectancy of down time if redundancy was not built in.
    Cy

    http://www.mashtronauts.com
    · Share on FacebookShare on Twitter
  • Options
    ilcram19-2ilcram19-2 Banned Posts: 436
    RS_MCP wrote: »
    On the DMVPN Router (Delay is 500, MTU 1500) IOS: 12.4 (23) Cisco 7206VXR
    On the Spoke Router (No Delay Configured, MTU 1400) IOS: 12.4 (15) Cisco 1841

    Cisco Bug: https://supportforums.cisco.com/docs/DOC-4046;jsessionid=434591C7BEB1642F61D82339C260F650.node0

    Any futher information, then please let me know.

    change MTU 1400 on both ends, i usually keep that the same on that spoke and hub
    change delay on spoke to 30 or less if you want the traffic to go only thru the hub or 100 if you want the tunnels to create dynamically to remose sites
    · Share on FacebookShare on Twitter
  • Options
    RS_MCPRS_MCP Member Posts: 352
    ilcram19-2 wrote: »
    change MTU 1400 on both ends, i usually keep that the same on that spoke and hub
    change delay on spoke to 30 or less if you want the traffic to go only thru the hub or 100 if you want the tunnels to create dynamically to remose sites

    Bearing in mind, I have multiple Routers with Tunnels that connect to the Hub. Changing the MTU on the Hub to 1400, could this not have an effect on exisiting Tunnels?

    Currently the Spoke does not have an delay configured, how will it help configuring a delay on the Spoke? Currently all traffic that requires services where the Hub (DMVPN Router) is passed down the Tunnel and it learns all remote subnets and sites vi EIGRP.
    · Share on FacebookShare on Twitter
  • Options
    RS_MCPRS_MCP Member Posts: 352
    Any update guys?
    · Share on FacebookShare on Twitter
  • Options
    ilcram19-2ilcram19-2 Banned Posts: 436
    the mtu size will only affect the tunnel interface that u apply it to, the tu size needs to be equal on both ends, also some routing protocols use mtu size to add neighbors
    · Share on FacebookShare on Twitter
  • Options
    RS_MCPRS_MCP Member Posts: 352
    ok, I have adjusted the MTU and IP TCP ADJUST-MSS settings to match eather other on the Hub & Spoke.

    Will continue to monitor the EIGRP neighbor relationship and see if any flapping occurs on the Tunnel Interface.
    · Share on FacebookShare on Twitter
  • Options
    RS_MCPRS_MCP Member Posts: 352
    Bad News, Tunnel still seems to be flapping after MTU and TCP ADJUST changes.

    Any other thoughts?
    · Share on FacebookShare on Twitter
  • Options
    ilcram19-2ilcram19-2 Banned Posts: 436
    also are u advertzing a default route over the dmvpn tunnel?
    · Share on FacebookShare on Twitter
  • Options
    burbankmarcburbankmarc Member Posts: 460
    what's the SRTT between to neighbors? Also, does this change a lot?
    · Share on FacebookShare on Twitter
  • Options
    RS_MCPRS_MCP Member Posts: 352
    ilcram19-2 wrote: »
    also are u advertzing a default route over the dmvpn tunnel?

    Yes the Hub Router has a default route to the spoke Tunnel router.
    · Share on FacebookShare on Twitter
  • Options
    RS_MCPRS_MCP Member Posts: 352
    burbankmarc wrote: »
    what's the SRTT between to neighbors? Also, does this change a lot?

    Could you explain what SRTT is please?
    · Share on FacebookShare on Twitter
  • Options
    deth1kdeth1k Member Posts: 312
    RS_MCP wrote: »
    Could you explain what SRTT is please?

    Use ip mtu path discovery on the tunnels, lower the mtu to 1462 and increase EIGRP hello to 30 sec. We have a lot of customers suffering from this issue, the above should help you.

    Cheers
    · Share on FacebookShare on Twitter
  • Options
    peanutnogginpeanutnoggin Member Posts: 1,096 ■■■□□□□□□□
    RS_MCP wrote: »
    Could you explain what SRTT is please?

    Pulled from the CiscoPress website, the SRTT (Smooth Round Trip Timer), is the number of milliseconds it takes for an EIGRP packet to be sent to this neighbor and for the local router to receive an acknowledgment of that packet.

    HTH.

    -Peanut
    We cannot have a superior democracy with an inferior education system!

    -Mayor Cory Booker
    · Share on FacebookShare on Twitter
  • Options
    RS_MCPRS_MCP Member Posts: 352
    deth1k wrote: »
    Use ip mtu path discovery on the tunnels, lower the mtu to 1462 and increase EIGRP hello to 30 sec. We have a lot of customers suffering from this issue, the above should help you.

    Cheers

    Hi, DETH1K, How will this command help me? I can see that I can enter this command from Global configuration mode, however, any "Show" commands I can use to see stats or results of any action for this command?

    Shall I lower the MTU on the Hub or Spoke, or both?

    What is the command to increase EIGRP "Hello" timing?

    Thanks for your help in advance.
    · Share on FacebookShare on Twitter
Sign In or Register to comment.