Help with configuring switch routes

[bricas2934]

Hello, i am practicing with packet tracer and making routes in switches. I configured the MLSW1 to connect to all 3 switches, but after i broke the connection from MLSW1 to SW3, PC3 no longer can ping PC2. 

I had made the ports trunk from SW1,2 and 3, but i don't know if i am missing something else? 

If anyone knows of any tips i could try, that would help a lot! 

Thank you

[David Ruess]

Hello,

If you were able to ping between PC3 to PC2 with the connection on the MLS but not able to once that connection was gone I would suggest 2 things to start:

1. Are all VLANS  on all switches. Even if a VLAN is not needed for an access port it must be created on every switch that traffic needs to flow through.

2. Does the MLS have a Default GW (assuming the PCs are in different VLANS) and can PC2/PC3 ping their default GW when you remove hat link between SW3 and the MLS.

If those check out can you provide the Switch configs for all 3 access switches and the MLS. You can upload them to a text file instead of pasting in here.

-David

[bricas2934]

I have attached my file to your comment. I am still learning so i could use any advice!

[Martin L]

you can attach PT file here in a zip format;

Regards, ML
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[bricas2934]

Thank you, i found out how to do that

[Martin L]

it seems to be ok; after a while, network has stabilized and PC got IPs; you can ping ok, all PCs ping each others ok. This delay could be PT fault as I had some issues when PT has many L2 links in the past.

Couple notes; Sw 2 is Root for vlan 20, which is ok; I would make MLS Root and see what happens - if u still have PT issues. (Add/force MLS as Root for vlan 1 for good measure as well)

As pointed above by David's note :"Are all VLANS on all switches"  If u want re-direct some vlan traffic then u could use switchport trunk allowed vlan add/remove/all/none command rather then not adding vlan x to switch.  This may not cause issues in real network with real gear but it may in PT (is just a simulator; not real IOS);

Note: because of L2 switching delays, PC are not getting IPs; you must wait a bit or force ipconfig /renew

Regards, ML
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[Martin L]

Wait until all switch ports are "green",a aka forwarding; then do ipconfig /renew and Ping all PCs. it works for me

For link redundancy  -in case of link/switch failure- add all vlans as mentioned by David

Regards, ML
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[bricas2934]

Pings work fine when all connections are up and running, but lets say i broke the group 3 connection, I am trying to configure the alternate route for when "group 3" is gone. It could then take the route from either:

PC3 - SW3 - SW1 - SW2 - PC2 

or

PC3 - SW3 - SW1 - MLSW1 - SW2 - PC2

Thank you

[Martin L]

your redundancy does not work now because you are missing vlans; all vlans should be present on all switches so when a link or a switch goes down, STP calculates new ports or even new Root switch if needed.  Add "missing" vlans on all switches

Regards, ML
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[bricas2934]

Since I made some ports i thought would work trunk, does not work? And when you say i have to add vlans to the other switches, is that adding vlans as in ports vlans 10,20 or 30? or is it adding it a different way?

Thank you

[Martin L · Accepted solution]

yes, add vlans manually with vlan 10 command in global config mode; repeat for vlan 20 and 30. 

before adding look at output of show vlan brief and show interface trunk;  it should tell u which vlans are missing; vlan missing on trunk means there is no STP for that vlan . also no traffic belonging to "missing" vlan will pass thru the switch. 

Regards, ML
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[bricas2934]

I did the simple command to add the vlans to each switch other than the vlan that is on that switch already and that worked. I just typed in "vlan 10" "vlan20" etc on the switches in config mode. Now after i break "Group 3" connects, it works like i planned.

Thank you for your help!