01-13-2018 09:48 PM - edited 03-08-2019 01:24 PM
question is attached below. what is the answer ?
Solved! Go to Solution.
01-14-2018 03:52 AM
No, this default gateway is not for InterVlan routing. Now Switch SVI VLAN 1 is working same as your system NIC. It should be aware, If It doesn't have routing information (except local subnet) then where the packet will send. So Default gateway is telling to switch is this is your default route.
Regards,
Deepak Kumar
01-13-2018 10:31 PM
01-13-2018 10:55 PM
if the default gateway is not assigned for host B then how it can ping A and C ?
01-13-2018 10:57 PM
01-13-2018 11:00 PM
ok if switch is not assigned Default Gateway how host B can ping host A or C ?
01-13-2018 11:29 PM
yes. it is L2 device so if host A ( VLAN-1 ) needs to ping host B ( vlan 32 ) , the intervlan routing should occur in the router interface.so the packet needs to leave the switch. how can that happen without any default gateway assigned to switch ?
01-14-2018 12:02 AM - edited 01-14-2018 12:10 AM
Hi,
you are confused between switch's L2 mode and L3 mode. While a switch will in L2 mode, it will take packet forwarding decision based on the MAC Table and L3 mode is taking a decision on the routing table.
So in your case, When Host B (VLAN 32) sending a packet to the router and router forwarding this packet to Host A (VLAN 1). Now your switch is not aware of the source and destination IP address, It is having MAC address in the MAC table and sending a packet to Host A and vice versa based on your L2 header of the packet.
Now Switch is having manageable IP in VLAN 1 and you are trying to access from Host B (VLAN 32). Now router is forwarding packet to switch SVI and switch is not aware of the source IP address, which is in the packet and not aware of his gateway (L3) device. So packet dropped at the switch itself. (here, Switch MAC table will not be working because it should be replying to the l3 address).
Regards,
Deepak Kumar
01-14-2018 12:13 AM
the question says
1.the host B can ping host A and host C
2.the host B can not telnet to Switch
your answer to resolve this issue is to configure default gateway in switch B.
so now my question is how intervlan routing can occur without a default gateway.
01-14-2018 12:18 AM
01-14-2018 01:09 AM - edited 01-14-2018 01:14 AM
for intervlan routing
1. need to configure sub interfaces in router
Router(config)#int fa0/0.1 Router(config-subif)#encapsulation dot1q 10 Router(config-subif)#ip address 11.1.1.1 255.255.255.0
Router(config-subif)#no shut
2.need to assign ip address for vlan
switch(config)#int vlan 1 switch(config-vlan)#ip address 10.1.1.1 255.255.255.0 Router(config-subif)#no shut
3.configure ip default gateway on switch
swi
switch(config)#ip default-gateway 11.1.1.1
Are my 3 steps correct for intervlan configuration ? ( just the steps. i used random ip addresses )
01-14-2018 01:20 AM
01-14-2018 01:29 AM
my question is do we need step-3( default gateway ) for inter-vlan routing ?
01-14-2018 03:52 AM
No, this default gateway is not for InterVlan routing. Now Switch SVI VLAN 1 is working same as your system NIC. It should be aware, If It doesn't have routing information (except local subnet) then where the packet will send. So Default gateway is telling to switch is this is your default route.
Regards,
Deepak Kumar
01-14-2018 05:52 AM
yes i got it now. thank you very much for helping me to figure it out.
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