how Telnet or SSH happens without default gateway

[Dinakaran Nagarajan]

We have a 6509 series of core switches and 3750 series of L2 switches,
There is no default gateway or any static routes to any IP.

VLAN 1 is made admin down and another vlan is used for all communication here in this environment

Please find the attached configuration for reference

But still iam able to take telnet or SSH.

I want to know how telnet or SSH or tacacs authentication happens without any static or default route.

[John Blakley · Accepted solution]

You only need a default gateway if you're coming from a subnet that the device doesn't know how to get to. Otherwise, if you're on the same subnet or a subnet that the core switch knows is connected, then you won't need a default gateway on your device. Your host on the other hand will need to know a default if you are trying to go to a different subnet than what your host thinks is local, otherwise it will arp for the mac address and send the traffic directly. The ip address on the L2 switch is only for management and doesn't influence traffic forwarding at all.

HTH,
John

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[glen.grant · Accepted solution]

  I don't see where they have turned off proxy arp on the L3 interfaces so it is probably using proxy arp to resolve the gateway . 

[ferdelriomex]

Hi Dinakaran, I agree with john blakley, you only need establish and use the default gateway if you try to connect from one pc ( via telnet or ssh ) and the device at wich you are trying to connect is on a different net segmnet, if both ( your pc and the router for example ) are on the same network segment, you dont need use the default gateway, on the orher hand, if your pc and the router are on different net segment, in this case you need to configure the default gateway in order to can establish comunnication between them.

Really hope that this can help you

Regards

[Kyle McKay]

I agree with Glen - it is most likely relying on Proxy ARP to forward the packets beyond the local ethernet segment.