Hey,

Can the default gateway of a host pc be in a different subnet than the host pc? For example, let's say a host pc has IP address 192.168.1.10 /24 and the router has sub-interfaces in the LAN with IP addresses 192.168.1.1 /24 and 172.20.20.1 /24. Can the host pc's default gateway be 172.20.20.1 /24?

Thanks...

No.

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blog.brokennetwork.ca

So why did this work in Cisco Packet Tracer?

Because proxy arp was probably enabled

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www.mellowd.co.uk/ccie/

I don't know if Packet Tracer has the ip proxy-arp command.....

So when the pc (192.1681.10) ARPs to its default gateway (172.20.20.1), can the default gateway send an ARP reply because the MAC address of the 172.20.20.1 sub-interface on the router is the same as the Fa0/0 interface?

I don't know how the default gateway can be in a different subnet. This does not make sense to me and yet it still works. I think it's an issue with Packet Tracer.

ip proxy-arp is a default so unless you entered no ip proxy-arp it will be on.

-Otanx

Yeah, you're right.....it does have proxy arp.

DSL_Modem#show ip interface fa 0/0.192
FastEthernet0/0.192 is up, line protocol is up (connected)
Internet address is 192.168.1.1/24
Broadcast address is 255.255.255.255
Address determined by setup command
MTU is 1500
Helper address is not set
Directed broadcast forwarding is disabled
Outgoing access list is not set
Inbound access list is not set
Proxy ARP is enabled
Security level is default
Split horizon is enabled
ICMP redirects are always sent
ICMP unreachables are always sent
ICMP mask replies are never sent
IP fast switching is disabled
IP fast switching on the same interface is disabled
IP Flow switching is disabled
IP Fast switching turbo vector
IP multicast fast switching is disabled
IP multicast distributed fast switching is disabled
Router Discovery is disabled
IP output packet accounting is disabled
IP access violation accounting is disabled
TCP/IP header compression is disabled
RTP/IP header compression is disabled
Probe proxy name replies are disabled
Policy routing is disabled
Network address translation is disabled
WCCP Redirect outbound is disabled
WCCP Redirect exclude is disabled
BGP Policy Mapping is disabled
DSL_Modem#

Thanks mellowd

Thanks Otanx

Hey can you please help me? I am using packet tracer and trying to configure default gateway on my PC. How do i define mask for it? which tab should i do it on? My def gw is 172.16.10.1/24...I am not able to figure out how to add mask?
Thank you !

you dont need to enter the mask for default gateway, just the ip address of the default gateway.

mask is only needed for the pc ip address.

But i think its taking mask as 255.255.0.0 since its class b ip address..and i am not able to reach gateway

post configs then?