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02-21-2020 05:25 PM - edited 02-21-2020 05:29 PM
Two default routes on HP 8206ZL switch
I need some help configuring a backup default route in a 8206ZL switch. This switch is our Core switch and it is connected to 2 different routers, each with their own uplink to the internet. The primary default route is configured as: ip route 0.0.0.0 0.0.0.0 <router1>
In the routing table it shows up as metric 1 and distance 1.
What I am used to from Cisco gear is that whenever you install a secondary default route, you can do so by specifying a higher metric value. So in case the physical line to router1 goes down, the route is removed from the routing table and the second lowest metric is installed. However, this switch does not allow me to change the metric value of static routes. The only thing I can change is the distance value. So I tried installing the 2 routes as follows:
ip route 0.0.0.0 0.0.0.0 <router1>
ip route 0.0.0.0 0.0.0.0 <router2> distance 20
Now, when we do a test by physically disconnecting the link to router1, nothing happens. The switch, even though the physical link is down, keeps the route to router1 in its routing table. It does not swap it out for the distance 20 route. As I said, I cannot change the metric value. We did confirm that we can ping the router2 interface from an office computer. So VLANing and routing between the "office <-> Core switch <-> router2" is working properly.
How do I go about this so that I can install my secondary route to the internet?
02-24-2020 01:43 AM
Re: Two default routes on HP 8206ZL switch
The configuration with different distances should be OK.
How exactly are you disconnecting the router1 from the switch? Do you disconenct the port on the switch? Has the VLAN that connects the 8206zl with router1 only a single member port on 8206zl or multiple ports?
This document describes a similar scenario
If the switch’s path to the preferred next hop router is broken in the middle of the intervening Layer 2 infrastructure, the switch will not inherently fail over to the backup static route statement. Instead, it will continue to send traffic to the next hop router’s MAC address until its ARP table entry ages out, and then deem the “destination network is unreachable” with the result of dropping the routed traffic.
If both routers are ProCurve yl/zl Switches using a dedicated transit VLAN with a single member port, the Uni-Directional Link Detection (UDLD) feature can detect the connection break between routers and block their interfaces within 15 seconds of the event. With the only member port disabled, the switch will disable the transit VLAN and remove the preferred static route entry from the route table. The static route with the next lowest administrative distance will then populate the route table, and connectivity should be restored.
That means for me that the switch will continue tying to use the route to router1 if the VLAN interface leading to router1 is up (it has at least one physical member port in up state) and it has an ARP entry.
Immediate failover will happen only if the transit VLAN interface connecting with router1 goes down. So it would be good if a dedicated VLAN is used for the connection with the default routers.