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New Member

eth -> ser interfaces ping times too high

While I was troubleshooting some low latency with some of my routers, I found out that ping times between the serial and ethernet interface is 44ms or even higher.

I would think the times would be around 1-2ms and not over 40ms!!! What could be the cause?

I'm talking about a 1601R with a T1 with a csu/dsu ver 12.0(3) and 8mb on board and 4mb flash pcmcia.

and on a 1751 v12.2(2)w/32mb on board and 16mb flash ping times are 104/115/144 ms

this is the first 2 lines of show processor cpu:

CPU utilization for five seconds: 0%/0%; one minute: 0%; five minutes: 0%

PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process

1 4 2073768 0 0.00% 0.00% 0.00% 0 Load Meter

2 356 216 1648 0.16% 0.14% 0.08% 6 Virtual Exec


Elliott Bujan

Initial Tropical Plants


Re: eth -> ser interfaces ping times too high

You can't really use the interfaces as a ping test as the router gives a very low priority to ping response . You need to ping thru these interfaces , get a device off the router and ping thru these interfaces to another device on the other side to get a more accurate view . I have seen on layer 2 switches if you ping 2 different switches interfaces on the same vlan I have seen it at least 20 ms so pinging from one interface to another is not a good test , use devices that are hung off each side as ping test points. I have seen this documented on CCO also .

New Member

Re: eth -> ser interfaces ping times too high

Thanks Glen.

I knew that ping has a low priority in traffic but I didn't think that these ping times could be this high.

I did ping other devices as well on the LAN and across the WAN and they came up fine (my normal ping times are around 30-40ms). My problem is still unresolved since there are periods when latency goes up the wall, with ping times aroun 4000 ms or sometimes even more.

any ideas on where I should be looking at? I'll keep digging.

Thank you for your suggestions.



Re: eth -> ser interfaces ping times too high

At the time you are experiencing the high latency take a look at your serial interface on both sides . It sounds like your serial interface is either tx or rx a high load , do a sh int serial x and look at the load ,

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