WEIRD ping results on interfaces
Mitch Comstock
I have a Cisco 4000 with 2 ethernet and 2 serial ports. If I telnet to the
router and ping each port, here are the results:
Ethernet0:
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 = 1/3/4 ms
Ethernet1:
Sending 5, 100-byte ICMP Echos to 206.112.201.33, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
Serial 0:
Sending 5, 100-byte ICMP Echos to 206.112.199.134, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 52/65/104 ms
Serial 1:
Sending 5, 100-byte ICMP Echos to 172.31.1.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 196/196/200 ms
Why is it taking so long to get a response back from Serial 0 and Serial 1?
They are inside the same box that E0 and E1 are on, shouldn't they be just
as fast? And why is Serial 1 so much slower than Serial 0?
FYI the 2 Ethernet ports are 10 Mb/s, Serial 0 is connected to a Adtran
128k Frame-Relay TSU, and Serial 1 is connected to a Adtran T1 TSU, both
via V.35 cables. A 'show ip route' indicates that the router knows that
the networks on each of these interfaces is directly connnected, routing
protocol is IGRP.
TIA
Mike Yelland
The packet doesn't go anywhere (who would answer ARP or bounce it
somehow?) except for internal to the box, and I'll bet there is a
listening process on the S int (process) which doesn't have to process
packets as fast as a LAN int,,, makes sense to me !
tstanley
When you ping a Cisco Serial the ping actually leaves the box on the link
and returns. Works great to test to loops too.
Mitch Comstock wrote in message <01bd68b9$da179920$9301010a@mscomstock>...
>I have a Cisco 4000 with 2 ethernet and 2 serial ports. If I telnet to the
>router and ping each port, here are the results:
>
Kevin Oberman
"Mitch Comstock" <mcom...@gails.com> writes:
> Why is it taking so long to get a response back from Serial 0 and Serial 1?
> They are inside the same box that E0 and E1 are on, shouldn't they be just
> as fast? And why is Serial 1 so much slower than Serial 0?
When you ping a serial line, the packet is actually echoed from the
remote end as is the response. A serial line is full duplex and the
receive lines can't see what is on the transmit lines. the packet is
sent to the remote end which routes it back to the router. The echo
reply is than sent back via the remote end. So the far end of S1 is
further away than S0. If you ping the far end address, the delay
should be about half of the delay pinging the local address as it only
has to make the round trip once.
Ethernets read their own data, so the delay is very low.
--
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest Orlando Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: obe...@es.net Phone: +1 510 486-8634