Issue with Cisco 892 router and 2950 48 port switch

[gkrl824@]

Ok, I'm a bit new to Cisco and networking and actually working with another vendor on this issue. The vendor has access to the Cisco 892 router and I have access to the 2950 switch.  The issue is they make a change on the 892 which I was told is trunking Interface 0 to allow all VLAN traffic, then any device connected to the 2950 switch just loses all access to the network/Internet.  Once they revert those changes on the 892, anyone plugged into the 2950 is working and has Internet. 

The way I understand is the Cisco 892 Interface 0 then plugs into a Unifi switch. Not sure which port. Then Port 2 on the Unifi uplinks to Port 34 on the 2950.  There is a VLAN 200 on the Unifi and I've configured VLAN 200 on the 2950 but not attached to any interfaces.  I did run this command "switchport mode trunk" on interface Fa0/34.  However, once they make that Interface 0 a trunk port, anyone plugged into the 2950 loses network/Internet.  The Unifi switch still works fine. 

Any help would be appreciated. 

Thanks

[marce1000]

                   >....then any device connected to the 2950 switch just loses all access to the network/Internet

                         - When that happens check the logs on the   2950 , see if anything comes up.

 M.

[balaji.bandi]

I do not believe anything do with CAt 2K Switch here, this is more config on another side. (Hope the switch doing just layer 2 here right ?)

worth looking this video :

https://www.youtube.com/watch?v=so_DM10V8M4

you need to get visibility of how the between devices are connected, so it's hard to suggest what is wrong.

How about user/device connected to unify works?

[paul driver]

Hello

---

gkrl824@ wrote:

The issue is they make a change on the 892 which I was told is trunking Interface 0 to allow all VLAN traffic,

---

So it sounds like this rtr perfroming the routing for your network, if it is then this interface will also have subinterfaces for vlan tagging.

892 rtr
int 0 < vlan 1
int 0.10 <vlan10
int 0.20 < vlan 20

So this mean the swithport of the 2950 IF it dirrectly connected to the rtr 892 NEEDS to be set as a trunk port NOT an access port.

However you mention a Unifi switch , now if this interconnected between the rtr and the 2950 then the setup should be
RTR <> Unifi ports < set as trunk
Unfi <> 2950 port < set as trunk>

ALSO your switch NEEDS to have the L2 vlans created on the switch that relate to the L3 subinterfaces on the rtr.

2950
Int x/x
description connecting RTR or Unifi switchport
switchport trunk encpasulation dot1q
switchport mode trunk

exit

vlan 10
exit
vlan 20
exit
etc...

[gkrl824@]

"2950
Int x/x
description connecting RTR or Unifi switchport
switchport trunk encpasulation dot1q
switchport mode trunk"

"However you mention a Unifi switch , now if this interconnected between the rtr and the 2950 then the setup should be
RTR <> Unifi ports < set as trunk
Unfi <> 2950 port < set as trunk>"

Yes, correct. it's basically Router - Unifi switch -  2950

I understand the ports need to be configured as a trunk. 

My understanding is that the Unifi ports are set as trunk for default. Since the vendor set the trunk port on the Router, then

I need to set the trunk on the 2950 as you mentioned. I thought I did, but forgot "switchport trunk encapsulation dot1q".

One more piece is that on the router the vendor configured Int 0 as trunk and VLAN 200.

I have already configured vlan 200 on the 2950 but not configured any interfaces. Do I need to?

I read that by default a trunk port sends traffic to and receives traffic on all vlans.

[balaji.bandi]

One more piece is that on the router the vendor configured Int 0 as trunk and VLAN 200.

I have already configured vlan 200 on the 2950 but not configured any interfaces. Do I need to?

I read that by default a trunk port sends traffic to and receives traffic on all vlans

is this VLAN 200 is native VLAN ? if the switch is acting like Layer 2 , Layer 2 VLAN crearting good enough on 2960

to check VLAN is spanned, show spann vlan 200, you can see where the root bridge for the VLAN (on both the sides)

is this only VLAN in the network.  yes when you set trunk all the vlan allowed by default, but if the trunk setup as access vlan 200 or allowed vlan 200, it will only allow that vlan.

[paul driver · Accepted solution]

Hello

---

gkrl824@ wrote:

Yes, correct. it's basically Router - Unifi switch -  2950
One more piece is that on the router the vendor configured Int 0 as trunk and VLAN 200.

---

I am assuming it is then it as I have explained above  physical interface with sub-interfaces

---

gkrl824@ wrote:

I have already configured vlan 200 on the 2950 but not configured any interfaces. Do I need to?

I read that by default a trunk port sends traffic to and receives traffic on all vlans.

---

Okay so if you are ONLY going to use vlan 200 and no other vlans then the interconnecting port between the Unifi<.>Switch can be an access port in vlan 200 and NOT a trunk- However if you are using multiple vlans then you need to make sure Unifi<.>Switch intercnnecting port is a trunk and they parity with each other, then it would be just a matter of configuring your access ports for your end hosts.

int x/x
description access port
switchport host
switchport access vlan x

[gkrl824@ · Accepted solution]

2950
Int x/x
description connecting RTR or Unifi switchport
switchport trunk encpasulation dot1q
switchport mode trunk

@paul driver

sorry for the late response since I had to coordinate with the vendor, but we finally got it working correctly and at least on my end, just needed to run the above command. Once the vendor made some changes on the Cisco 892 router, we were able to access the Guest network on VLAN 200.  

Thanks