how to give gateway to hosts which are connected two routers(layer3 switch)?

Question

I have three networks(Building A 175.166.0.0/23, Wireless Access point 10.1.1.0/24, Bulidng B 175.165.0.0/16) connected to two Layer3 switch Dell 6024.

175.166.0.0/23 --- Layer3 siwthc A -- 10.1.1.0/24 -- Layer 3 Switch B----175.165.0.0/16

Between two building(two netwroks 175.166.0.0/23 and 175.165.0.0/16) are two Air link DWl-7700AP wireless access point. The data pass two buildings have to go through those two wirless access point. I gave ip address to wireless access point device (10.1.1.11 and 12, 255.255.255.0, the gateway 10.1.1.1). The Layer 3 route ip configured the folowing:

Layer 3 Switch A:

console# show ip route
Maximum Parallel Paths: 4 (4 after reset)

Codes: C - connected, S - static, R - RIP, O - OSPF, E - OSPF external

S 0.0.0.0/0          [1/1] via 175.166.0.2 45:12:21             vlan 1
C 10.1.1.0/24        is directly connected                        g3
S 175.165.0.0/16     [1/1] via 10.1.1.1 98:50:5                 g3
C 175.166.0.0/23     is directly connected                        vlan 1

console#

Layer 3 switch B:

console# show ip route
Maximum Parallel Paths: 4 (4 after reset)

Codes: C - connected, S - static, R - RIP, O - OSPF, E - OSPF external

S 0.0.0.0/0          [1/1] via 175.165.0.2 100:0:56             vlan 1
C 10.1.1.0/24        is directly connected                        g3
C 175.165.0.0/16     is directly connected                        vlan 1
S 175.166.0.0/23     [1/1] via 10.1.1.2 99:53:42                g3

console#

This set up worke fine execpt one thing:from hosts in building A (175.166.0.0/23) can not access thoes wirelee access point(Some IT guys need access for management purpose.) I think problem is that those two wireless devices' gateway were set up point to building B layer 3 switch

(10.1.1.1). Hosts from building B(175.165.0.0/16) can access those two wireless access point. From layer 3 switch A, I can ping those two devices and 10.1.1.1 whichis interface of layer3 switch B. However, from any hosts in 175.166.0.0/23 network can not ping those three IP. My question is how to give gateway to hosts which are connected two routers(layer3 switch)? which router should they point to?

Thanks a lot

Shawn

ToeSide · Answer

Hi Shawn, I'm finding it a bit hard to follow and understand your issue. But what I think your saying is Access Point 10.1.1.11 has it's default gateway pointing to L3 switch B for it's routing? Unless there is some specific reason for this then yes I would suggest using Switch A for it's routing (i.e. it's next hope). Try this and let me know how you get on.

xbi · Answer

Here is the map:   A network-------L3 Switch A--------Wireless Access point A-------point B--------L3 switch B-------------B network   A network: 175.166.0.0/23 wireless Access Point A: 10.1.1.12 Wireless Access Point B: 10.1.1.11 B network: 175.165.0.0/16   The problem is that if both  Access Point 10.1.1.11 and 12 has it's default gateway pointing to L3 switch B for it's routing. B network can access it(manage web server) but A network can not. If both Access Point 10.1.1.11/12 has it's default gateway pointing to L3 switch A for it's routing. A network can access it, but B network can not.     In genernal, my questions is that if the hosts in the network which connected two routers, which router should be the gateway for hosts to route or doesn't matter. Either one should be ok.  I know, in most case, you use serial interface to link two routers, and therre is not any hosts except two serial interface connected toghter.     Thanks   Shawn

ToeSide · Answer

Alright I think I understand what your trying to achieve. You need to set the default Gateway of each wireless device to it local L3. Ie. Wireless Point A to Network A and Wireless Point B to Network B. This way all traffic will have a route across the entire network. You will also need static routes on the L3 switches (Network A to B and visa versa) so they can communicate with one another. I think the reason you had both Access Points Gateway to one L3 switch was for the final default route? This will still be achieved from the above configuration. If your still having problems after the changes can you post routes and configurations?   Thanks

xbi · Answer

I have posted the static route configuration of L3 switch in my first question. In current configuration, the network traffic can be routed between two networks. All host in network A can communicate to all hosts in network B and visa versa.     The only problem are those two wireless access points which are link two networks. There are web interface prebuild into those two device, so you monitor  and manage the those devices. If you let both device'sgateway point to L3 switch B, only hosts in network B can access the web interface and manage it. Hosts in network A can not.  As you suggest, wireless access point A gateway point to L3 switch A and Wireless access point B gateway point to L3 switch B, This way, hosts in network A can only access wireless point A but not B, and hosts in network B can only access wireless point B but not A. I want all hosts in two networks can access web interface of those two wireless access point.   This is very special configuration. In most cases, hosts(computers, printers, other network devices) are connected siwtchswitchswitch link other hosts. In here, two wireless access point are acting a bridge to connect two network.        A network-------L3 Switch A--------Wireless Access point A-------point B--------L3 switch B-------------B network   A network: 175.166.0.0/23 wireless Access Point A: 10.1.1.12 Wireless Access Point B: 10.1.1.11 B network: 175.165.0.0/16   For example, lets assuem both gateway of wireless access point device are pointed L3 switch B. One hosts(175.165.0.100) in network A want to communicate wireless access point A, L3 switch A router the message to point A. Point A want reply back, sine the IP is not in same subnet, then point A send message to L3 switch B since it is gateway of point A. L3 switch B look the IP and it is from network A, and it will send to network A. Here( I am very confused)  the message has to go back to wirless access point A in order to back to netowrk A . I am not sure wether the problem is here.   Thanks   Shawn

ToeSide · Answer

Hi Shawn,

Sorry for the delayed response but decided to setup your scenario in the lab as to avoid any more confusion...took me a while to ‘borrow’ the required equipment...

I had setup your network and was unable to connect to the wireless access points as you described. So these are the changes I made for the network to operate correctly.

As I said previously set each Gateway of the access points to their local L3 switch. i.e Access point A’s gateway is 10.1.1.1 (the ip address of Switch A ethernet port) and

Access point B’s gateway is 10.1.1.2 (the ip address of Switch B ethernet port)

Secondly set up a static route on each switch

Switch A

ip route 175.165.0.0 255.255.254.0 10.1.1.2

Switch B

ip route 175.166.0.0 255.255.0.0 10.1.1.1

That should do it....

xbi · Answer

Hi, Sorry I don't know your name, just call you Toe Side Thank you very much for trying to help me. Since this whole set up is already in production, I have to wait for off time to make some change, probably this Saturday, I will let you know the result.  In the meantime, what is routering knowledge behind your set up? Both wireless access point device in same subnet, why can they both point to same L3 switch( kind of like router)? Is this because the wireless bridge thing?   Anyway, Thanks a lot   Shawn

Networking General

how to give gateway to hosts which are connected two routers(layer3 switch)?

Was this post helpful?