VLAN trunking issue

[Sandip Barot]

Hi There,

We have few VLANs span across 2 cisco 3750 switches.  Switch1 and Switch2. 

Configuration for both the switches is attached.  VLANs across switches is accessible with the following issues.

1. The switch 2 can not ping VLAN Interface IP of switch 1 and viceversa. 

2. If any VLAN defined on switch2 , it is not getting accessible from other VLANs. but switch1 VLANs can be accessed .[ie vlans 22,50,60 and 80 can be accessed across switches but vlan33 cant be accessed]

Thanks 

Sandip

[Reza Sharifi]

Hi,

switch 2 does not have any default route or default gateway defined.

ip route 0.0.0.0 0.0.0.0 10.10.30.x where x is the gatway for this subnet

 HTH

[Sandip Barot]

Thanks for the suggestion.  However, even after adding default route (and related VLAN for the default route) it doesn`t work.

updated config for switch2 and basic diagram of connection attached.

[Deepak Kumar]

HI,

Both switches having "IP Routing" command enabled. So you must have disabled the "IP Routing" from the 2nd switch (access switch). It will start working. 

Command:

No ip routing

[Sandip Barot]

tried that but it is not having any effect.

[balaji.bandi]

Can you able to ping from 1.99 to 10.10.30.254  ( if this working, then this could be an issue with PC have FW ? building, what OS is this PC ?)

interface Vlan33
ip address 10.10.30.254 255.255.255.0

can you post from bot the switches show ip route

[paul driver · Accepted solution]

Hello

sw1

doesn’t have any vlan33 ip addressing 

also enable ip routing 

sw2 

disable ip routing and give it an default gateway of Sw1 vlan33 ip address 

[Sandip Barot]

With below config it works : ie each vlan PC communicate with different VLAN PCs. and switches can ping VLAN Interface IPs.

- Sw 1 gave VLAN33 ip address (10.10.30.1)

- Sw2 disable IP routing and set VLAN33 ip address of sw1 (10.10.30.1) as default gateway.

Configured 10.10.30.x LAN default gateway as sw1 VLAN33 ip address (10.10.30.1)

******

However, here the question is why we have to give Gateway address for VLAN33 PCs as Sw1 VLAN33 Ip address ?  This way it has to traverse to the Sw1 always if need to communicate with other VLAN.

-Why VLANs configured on Sw2  in the same way as Sw1 doesn`t work and we need to direct default route to Sw1 to make it working ?

[Reza Sharifi · Accepted solution]

However, here the question is why we have to give Gateway address for VLAN33 PCs as Sw1 VLAN33 Ip address ?  This way it has to traverse to the Sw1 always if need to communicate with other VLAN.

That is correct. In this case, sw2 is simply a layer-2 device with one ip for management only and sw1 is doing the routing between vlans.  If for redundancy you want both sw1 and sw2 to do the routing for you, then you have to make sure there is trunk link between the 2 switches and then run hsrp or vrrp on both switches. That way switch is the active router and the other switch is on standby. 

-Why VLANs configured on Sw2  in the same way as Sw1 doesn`t work and we need to direct default route to Sw1 to make it working ?

Again sw2 is just layer-2 and that one IP you gave it is for managing the switch itself but all the inter-vlan routing is done on sw1. Also, on sw2, the reason that you need to have a default route to sw1 is that other subnets can reach sw2. Again this IP on sw2 is just for management, so you can telnet or ssh to the switch.

HTH