DMVPN Tunnels with EIGRP
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
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
Comments
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keenon
Member Posts: 1,922 ■■■■□□□□□□
if its a known bug in the IOS version your using your choices are limitedBecome the stainless steel sharp knife in a drawer full of rusty spoons -
burbankmarc
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. -
ilcram19-2
Banned Posts: 436
what is the delay and MTU size setup on the tunnel interface spoke and hub? -
RS_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. -
Cyanic
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. -
ilcram19-2
Banned Posts: 436
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 -
RS_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. -
ilcram19-2
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
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RS_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. -
RS_MCP
Member Posts: 352
Bad News, Tunnel still seems to be flapping after MTU and TCP ADJUST changes.
Any other thoughts? -
RS_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. -
RS_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? -
deth1k
Member Posts: 312
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 -
peanutnoggin
Member Posts: 1,096 ■■■□□□□□□□
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.
-PeanutWe cannot have a superior democracy with an inferior education system!
-Mayor Cory Booker -
RS_MCP
Member Posts: 352
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.
