Strange ARP behavior

TitinhoTitinho Member Posts: 15 ■□□□□□□□□□
in CCNA & CCENT
Hi, this is the situation I was setting up my lab in the following way (in this case I am only using 1 cat 2950, 1 2650 router and my ISP router (a netgear CG3100):

I assign ip address 10.255.255.12/24 to my SW and I connect my ISP router to SW 1 and assign it to VLAN 100, I then configure the 2650 router in "router on a stick" with 10.255.255.1 address.

The thing is, I do not configure a default-gateway on my switch, but I am still able to ping my ISP router that is on a different network.

Using a monitor session on the port connected to the 2650 I notice that the 2950 sends an ARP requesting "192.168.1.1 tell 10.255.255.12" and the 2650 responds and from that point on I can ping the ISP router

now, what I dont get, is why is the SW sending an ARP request for a address outside of its network, why is the 2650 responding to an ARP request that is not its own ip, and how can my netgear router respond to the ping, when I use a other router instead if the netgear one, the ping fails (unless I set a default route on the "other" router)


I hope you can understand what I typed, English is not my native language
· Share on FacebookShare on Twitter

Comments

Sign In or Register to comment.