02-02-2019 06:58 AM - edited 03-08-2019 05:13 PM
I need to connect 3 buildings with redundancy but want to isolate the routing within each building as much as possible. Each building has a switch however only 2 buildings have layer 3 switches. THe L2 switch (R2) is a 2960 switch. I want to create an L3 link between R1 and R3 but Layer 2 trunks between R1 and R2 and R3 and R2. I guess an L2 trunk link between R1 and R2 should not be a problem since they share the same vlans. Not sure what to do between R2 and R3. How do I get this to work?
R1 (L3 switch)
vlans 1,2,3
interface fa0/1 ip 192.168.1.1 (L3 link beteen R1 and R3)
R2 (2960 L2 switch):
vlans 1,2,3
R3 (L3 switch):
vlans 1,4,5,6
interface fa0/1 ip 192.168.1.2 (L3 link beteen R3 and R1)
Solved! Go to Solution.
02-02-2019 07:24 AM - edited 02-02-2019 07:30 AM
Hi,
Technical speaking, you can still build the trunk between R3 (VL 1,4,5,6) and R2 (VL 1,2,3) even through they use different VLAN. At a result, only VLAN 1 would use the trunk between R3 & R2. Therefore, VLAN 2,3 cannot have the benefit of network redundancy (E.g. when R1 is down, the VLAN 2,3 on 2960 would also down). So, you could create VLAN2,3 (not SVI, just VLAN) on R3 as well to solve this single point of failure.
Beside, I see you emphasized the "layer-3", may I know if your L3 switch is acting as network gateway for those VLANs? If true, you should consider to use HSRP / GLBP / VRRP. After that, you need to check if there is any single point of failure. (E.g. enabled with GLBP, and if the link between R1&R3 has broken, is there any connectivity issue to outside network? ) Or to play safe, you could consider to setup trunk between R1 & R3 as well.
02-02-2019 07:24 AM - edited 02-02-2019 07:30 AM
Hi,
Technical speaking, you can still build the trunk between R3 (VL 1,4,5,6) and R2 (VL 1,2,3) even through they use different VLAN. At a result, only VLAN 1 would use the trunk between R3 & R2. Therefore, VLAN 2,3 cannot have the benefit of network redundancy (E.g. when R1 is down, the VLAN 2,3 on 2960 would also down). So, you could create VLAN2,3 (not SVI, just VLAN) on R3 as well to solve this single point of failure.
Beside, I see you emphasized the "layer-3", may I know if your L3 switch is acting as network gateway for those VLANs? If true, you should consider to use HSRP / GLBP / VRRP. After that, you need to check if there is any single point of failure. (E.g. enabled with GLBP, and if the link between R1&R3 has broken, is there any connectivity issue to outside network? ) Or to play safe, you could consider to setup trunk between R1 & R3 as well.
02-02-2019 07:26 PM
Thanks. Yes, R1 and R3 act as gateway for their own vlans. R1 and R3 do have SVI's created already for their vlans. The initial goal was to have L3 switches in all 3 buildings to contain routing or the local vlans within each building, however due to financial reasons this has changed.
HSRP / GLBP / VRRP. would require us to host all the vlans and both R1 and R3. And it does not really confine routing within one building.
Confiuring a trunk between R1 & R3 would make it a layer 2 domain again.
02-02-2019 07:56 PM
02-02-2019 02:32 PM
I believe this is school work/assignment.
If this is the case, please state so because you need to accept that answers provided may not be acceptable to your class instructor.
02-02-2019 07:29 PM
This is not a school assignment and not high priority.
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