Switching Advice

[avilt]

I have a requirement to implement routing among 3 locations as shown in the following diagram. Location A.B & C are in a unique subnet in default vlan1. I cannot make any changes on these networks (A, B & C) because it's not under my control. Now I am providing a 9300 L3 switch at central location with one single FO uplink to another common L2 switch. How can I enable routing among these 3 locations without making any changes on locations A, B & C?

[balaji.bandi]

There 2 Options :

1. Create a New VLAN Interface use point Point link and run OSPF and advertise the network, each switch can learn the routes from another switch. ( Hope the between switch is trunk link, so allowed new VLAN also in the trunk)

as you mentioned Layer 2 switch - but still (not know what model of the switch)

2. configure the uplink port as Layer 3 interface towards uplink and run IGP OSPF and EIGRP whatever your favorite and announce to local networks.

is this make sense? let us know if you like any configuration. ( so post the current running-config, let us know what port connected to link side)

[Joseph W. Doherty]

Do these locations route off their local subnet, currently?  If so, do hosts have a gateway IP or is the non-local subnet done via ARP?  How does a 192.168.1.0/24 host intercommunicate with a 192.168.3.0/24 or 192.168.3.0/24 host?

[avilt]

Right now there is no communication among these 3 locations and are on L2 switch. Routing protocol is not supported.

Also the FO link from L3 to other switch is a single FO link.

[balaji.bandi]

No routing protocol supported on any of the devices? but can you cerate L3 switch or SVI interface, then use static routing  ? is that works?

what is these devices or switch models?

[Joseph W. Doherty]

Are hosts configured with gateways or not?

[avilt]

Default Gateway is not yet configured, it is to be defined after setting up L3 sswitch.

[balaji.bandi]

if they are Locally communication same VLAN , switch do not required any default gateway required.

if you looking for them to interact with other switches, you need to make routing enable and make static Routing.

to give best suggestion as i have mentioned earlier, post all the device config, so we can tweak and suggest better

is this works ?

[MHM Cisco World]

the problem here as My view is native VLAN, VLAN 1 have different subnet than VLAN 1 in other SW.

[paul driver]

Hello

9300
ip routing
int X/X
Description FO link
ip address 192.168.1.254 255.255.255.0
ip address 192.168.2.254 255.255.255.0 secondary
ip address 192.168.3.254 255.255.255.0 secondary
no shut

Location clients
Provide each client in there repsective network a default-gateway to the related L3 address on 9300 switch