i get the purpose of this command. Its a default gateway so you can access the switch from another subnet. However i have a 2950 on the network and its pingable/telnetable from everyother subnet yet it has no ip defualt gateway configured. It is only a L2 switch. How can this be if it has no default gateway?
I have seen a behavior on some switches where they will arp for unknown destination addresses when they do not have a default gateway set, and I believe that the 2950 may be one of those switches. If the switch will arp for the unknown address, and if the connected layer 3 interface supports proxy arp, then the layer 3 gateway will send an arp response (with its own MAC address) to the switch. This allows the switch to access remote addresses without having a gateway configured.
It is best practice to configure a default-gateway on the layer 2 switch. But configuring a default-gateway is not an absolute requirement.
Rick is absolutely correct. My personal experience with 2950 series switches is that if the ip default-gateway is not configured, they will rely on ProxyARP for every IP outside their management VLAN. There are obviously numerous drawbacks to have a switch relying on the ProxyARP to communicate with outside world. Therefore, I believe, configuring the ip default-gateway is the correct thing to do.
As others have said someone has left proxy arp turned on at the layer 3 routing interface or SVI. This will allow your device to reached without a default gateway , that said best practices indicate it should not be on and you should use a default gateway statement on your devices. Reasons why proxy arp should not be used include
It increases the amount of ARP traffic on your segment.
Hosts need larger ARP tables in order to handle IP-to-MAC address mappings.
Security can be undermined. A machine can claim to be another in order to intercept packets, an act called "spoofing."
It does not work for networks that do not use ARP for address resolution.
It does not generalize to all network topologies. For example, more than one router that connects two physical networks.
We have 3 identical switches configured by someone else and would like to claim some of the Gigabit ports(G1/G2/G3/G4) for use on servers. When we try to change the wiring and configuration, we run in to connectivity issues. Attached is a des...
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...