Problem with transfer the packets between L3 and L2 Switches

[M-AHMED]

Hello everybody, I am just starting to create my LABO for an objective to pass the CCNA exam soon.

I have a little problem that the VLAN 99 Management is accessible for all L3 devices but cannot reach (L2 SW 01) Devices.

You will find attached my labo (Photos and running-config).

Thanks in advance

[Richard Burts]

I have looked at some of the configs. The first thing that I notice is that L3SW1 connects to the router and connects to the L2 switch. I would expect to find 2 trunks on the L3 switch, one connecting to the router and one connecting to the L2 switch. But I see only one trunk in the config.

[M-AHMED]

First of all thank you for your support. 

L3 SW01 Interface Gig1/0/23 is route interface and have an ip address same network of R1 Gig0/0 that's why it’s not on trunk mode. 

[balaji.bandi]

there are different way to solve the issue, Layer2 streched across all the switches, or use routed mode - you can mix both

Configure the L3 Switches  side interface as Trunk port and created a Layer3 SVI

if you like to use routing based then you need to have Layer 3 Interface in L3 switch for the MGMT VLAN, not on the router.

[M-AHMED]

Hello,

I modified that now all switches are accessible between them but when i try to reach them from another vlan i have a problem of gateway. you will find attached a photo of out layers.

[Richard Burts]

I do not understand the photo in this post. I do not understand what you mean when you say "I modified that now all switches are accessible between them" Perhaps you can explain this a bit more?

If the new configs do not provide access between vlans then perhaps you can post current copies of the configs which might help us identify the issue. It would also help us understand the issue if you would tell us "I have problems with access from this source address, on this device, to that destination address, on that device.

[M-AHMED]

Thank you for you answer.

When i said i modified it I wanted to say that i removed vlan 80 and now the interface Gig1/0/22 as you see on the screenshot is the gateway of Srv network.

the problem exact that all switches are reachable between them, even the router can ping the switches, but only Srv network that can ping L3 Switches but cannot ping the L2 Switches if i think the problem that L2 switches cannot find the gateway of Srv Network.

i hope iam clear for the explication

[balaji.bandi]

post show run from all devices again after modifing the config.

[M-AHMED]

Hello thank you for you support,

you will find attached the running config of the all the intermediate devices.

[balaji.bandi]

as i mentioned before there are different way to fix the issue.,

you need to Managment to reach across all devices, then you need to have Layer2 Trunk between Router and Switches (L3) then use router as gateway for all - so that management can reach all over.

make sure you have OSPF routing established and routing shared across network between OSPF peers. show ip ospf nei can help you.

show ip route can show you routing table.

[M-AHMED]

yes you are right, for all my past topology i tried this method and it's functionally i mean (you need to Management to reach across all devices, then you need to have Layer2 Trunk between Router and Switches (L3) then use router as gateway for all - so that management can reach all over.)

But this time I am trying to mastery L3 Switches because I never worked with it. I wanted to discover how it functions.

you will find attached route table and ospf nei.

Thanks in advance.

[balaji.bandi · Accepted solution]

Ok if you masering Layer 3, then you Layer 3 Gateway for the managemetn VLAN resides inside Layer3 Switch, May be connect Layer 3 switch and Layer 3 switch using trunk and run HSRP so you have gateway for the Management VLAN or P2P Link between Layer3 switch to exchange routes (if not all packets need to go to Router and transit from there)

[Richard Burts · Accepted solution]

Thank you for this information which does provide the reason that it did not work originally. When we configure a vlan it needs to have layer 2 reachability from one end to the other. But in your original config the client was in a vlan that extended to the layer 3 switch, but the connection from the L3 switch to router was a routed link. The router was configured with the gateway address for the vlan but did not have layer 2 connectivity to the other parts of the vlan.