Multilink 1 minute ping spikes

[ropeguru]

Morning all,

First time here so please be gentle.

I have a Ciscor 2600 Series router running IOS Version 12.2(4)T3.

Running Config for Multilink:

interface Multilink3
ip address xxx.xxx.xxx.xxx 255.255.255.252
no cdp enable
ppp multilink
multilink-group 3
!
interface Serial0/0
no ip address
encapsulation ppp
no ip mroute-cache
no cdp enable
ppp multilink
multilink-group 3
!
interface Serial0/1
no ip address
encapsulation ppp
no ip mroute-cache
no cdp enable
ppp multilink
multilink-group 3

What I am seeing is that right at about every 60 - 65 seconds a 200+ ms ping spike. Can anyone give me an idea as to what might be doign this??

Almost forgot to add that this is two T1's going into Verizon for internet access.

 

[IllegalOperation]

Monitor the CPU, memory, and overall bandwidth load.

Check the interfaces for input/output errors and drops.

What kind of routing protocol are you running?

 

[ropeguru]

Hi,

Thanks for the response. This is a very basic setup. CPU load and memory usage and bandwidth are all low, even during time of the spikes. We average only about 600k of data across these links at the moment. The ping spikes only last for a second, maybe two at the most. There are no errors or drops showing on the interfaces. Routing protocols are not being used. As I stated before, it is a very basic setup with all static routing.

Here is the entire running config:

Current configuration : 1334 bytes
!
version 12.2
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname router
!
logging monitor informational
enable secret 5 xxxxxxxxxxxxxxxxxxxxxxxxxxx
enable password xxxxxxxx
!
ip subnet-zero
!
!
!
!
!
!
interface Multilink3
ip address 141.xxx.x.xxx 255.255.255.252
no cdp enable
ppp multilink
multilink-group 3
!
interface FastEthernet0/0
ip address 141.xxx.xx.xxx 255.255.255.248
no ip mroute-cache
speed auto
full-duplex
no cdp enable
!
interface FastEthernet0/0.1
no cdp enable
!
interface Serial0/0
no ip address
encapsulation ppp
no ip mroute-cache
no cdp enable
ppp multilink
multilink-group 3
!
interface Serial0/1
no ip address
encapsulation ppp
no ip mroute-cache
no cdp enable
ppp multilink
multilink-group 3
!
ip default-gateway 141.xxx.xxx.xx
ip classless
ip route 0.0.0.0 0.0.0.0 141.xxx.x.xx permanent
ip route 10.xx.xx.xx 255.255.0.0 141.xxx.xx.xx permanent
ip route xxx.xxx.xxx.xxx 255.255.255.192 xxx.xxx.xxx.xxx permanent
no ip http server
ip pim bidir-enable
!
access-list 10 permit xxx.xxx.xxx.xxx
access-list 10 permit xxx.xxx.xxx.xxx 0.255.255.255
no cdp run


If I can provide anymore info, please let me know..

 

[JOAMON]

Couple of things to consider. You might put the following on your multilink interface:
ppp multilink fragment disable
depending on the version of IOS and model of router this may also read as:
no ppp multilink fragmentation

Also consider enabling IP CEF on both sides.

These may help.

I also have on my serial interfaces
no keepalive
no fair-queue

What purpose does interface FastEthernet0/0.1 serve?
Should also get latest 12.3 mainstream you can.

 

[JOAMON]

Just thought of something else.
Are these serial interfaces point to point connections or connections to your ISP. If point to point make sure to have one side set with the following:
service-module t1 clock source internal
could be a timing issue if neither side is doing the clocking.

 

[ropeguru]

Unfortunately I do not have access to the other side. That side is owned by Verizon. This is a router that we use for Internet access.

I will look at the multilink fragmentation and see if that might be causing something. I kind of think not as these spikes are very methodical and come at pretty much exact intervals.

COuld be the keep alive trying to do something and causing issues.

The Ethernet interface is the interface where all our internet traffic dumps into our local network. You have to remember this is an endpoint router at the customer premesis and not sitting in an ISP somewhere just routing packts from one serial interface to another.

 

[JOAMON]

Don't need to worry about clocking then as Verizon is doing that for you....would consider the other items I mentioned. I would only enable IP CEF for per destination and not per packet as there is more CPU load for per packet.