02-26-2009 12:19 AM - edited 03-04-2019 03:43 AM
I have a Cisco 3750 switch and there is no default gateway set on it.
SW01#show ip route
Default gateway is not set
Host Gateway Last Use Total Uses Interface
ICMP redirect cache is empty
SW01#show cdp ne
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID Local Intrfce Holdtme Capability Platform Port ID
CORE01 Gig 1/0/1 144 R S I WS-C3750G Gig 1/0/6
FASW01.local.com
Gig 1/0/3 155 S I WS-C3750- Gig 1/0/3
SW01#
SW01#traceroute 172.24.223.113
Type escape sequence to abort.
Tracing the route to 172.24.223.113
1 172.24.175.18 1007 msec 0 msec 0 msec
2 172.24.175.35 0 msec 0 msec 0 msec
3 192.168.107.117 9 msec 16 msec 17 msec
4 192.168.247.141 17 msec 8 msec 25 msec
5 192.168.247.142 17 msec 17 msec 33 msec
6 172.24.223.113 34 msec 17 msec *
SW01#
How is this possible for me to traceroute from a switch that isn't acting as a layer-3 device?
SW01#show ip int br
Interface IP-Address OK? Method Status Protocol
Vlan1 172.24.175.26 YES NVRAM up up
FastEthernet1/0/1 unassigned YES unset down down
FastEthernet1/0/2 unassigned YES unset down down
FastEthernet1/0/3 unassigned YES unset down down
<snip>
GigabitEthernet1/0/1 unassigned YES unset up up
GigabitEthernet1/0/2 unassigned YES unset down down
GigabitEthernet1/0/3 unassigned YES unset up up
GigabitEthernet1/0/4 unassigned YES unset down down
SW01#
Thanks,
John
Solved! Go to Solution.
02-26-2009 06:23 AM
172.24.175.18 has proxy-arp enabled (default setting) and it's handling any request from devices w/o gateway on that segment.
If you want to prove this concept, go to this device and disable proxy-arp then try communicating from the switch to other segments.
HTH,
__
Edison.
02-26-2009 01:09 AM
Do a "sh run | i ip default-gateway" and see whether you have anything setup
Narayan
02-26-2009 01:40 AM
Hello Narayan,
Here is the output:
SW01#sh run | i ip default-gateway
SW01#
I have never in my life seen a device do this without a default gateway.
Thanks,
John
02-26-2009 06:23 AM
172.24.175.18 has proxy-arp enabled (default setting) and it's handling any request from devices w/o gateway on that segment.
If you want to prove this concept, go to this device and disable proxy-arp then try communicating from the switch to other segments.
HTH,
__
Edison.
02-26-2009 07:35 AM
You are absolutely correct.
Thanks for the answer!
John
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: