From: Michael Snyder (msnyder@xxxxxxx)
Date: Sun May 12 2002 - 17:43:44 GMT-3
I've noticed something. Once in a while I ping the local (near)
interface ip address by mistake when I really want to ping the remote
(far end) ip address of the serial link. Anyway while Ethernet seems to
have the same ping times, near or far, Serial interfaces always seem to
have double the ping time.
I know from frame-relay that you have to map a local ip address to a
interface dlci in order to ping it. So when you ping an ip of a
frame-relay interface local to the router, your traffic is actually
traveling to another router, and coming back.
Here's the rub, assuming that when I ping a local serial ip address the
traffic is traveling to the far end of the link and returning, shouldn't
a local ping have the same round trip time of a far end ping?
Why is it double? What's up with that? Surely it's not two round trips
for a local ping.
BTW, I did some debugging on the far end of the serial link (router b).
I'm showing a single icmp type 8 redirect message, on my first local
ping, but that's it. I assume router A is caching the redirect, but the
ping times remain about double even after the first ping sequence, and
those interface lights on the far end router (b) light up every time I
do a local interface ping on router (a) .
A#s
Interface IP-Address OK? Method Status
Protocol
Serial0 10.1.1.1 YES manual up
up
A#
A#ping 10.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 68/70/80 ms
A#ping 10.1.1.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/35/36 ms
A#
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