Keepalive is not allowed on switchport interface

[walee]

Hi,

I got a Cisco6513 with native mode IOS. However, the keepalive command cannot be set on VLAN or switchport interface (Ethernet). Is there any workaround to make the local interface down if the interface on remote site is down?

Thanks,

Walter

[Georg Pauwen]

Hello Walter,

I think the closest you can get to achieving your goal is to use the command:

errdisable detect cause link-flap

When the cause (a flapping-link in this case) is detected on an interface, the interface is placed in an error-disabled state.

Just keep in mind that you must enter the shutdown and then the no shutdown commands to recover the interface manually from errdisable, unless you configure the command:

errdisable recovery cause link-flap

as well.

HTH,

Georg

[tbaranski]

We'll need to know a bit more about your topology and what you're trying to accomplish. Is it the VLAN interface that you want to change state to "down", or the physical interface? Physical Ethernet interfaces do tend to change state to down when the adjacent interface is down, though with WANs it can be more tricky because there may be devices in between you and the remote site.

[walee]

Hi,

Yes, I want the VLAN interface to chanage state to "down" and I found that if the physical interface is down, the state of VLAN interface will also be down.

The WAN link is a Ethernet connection and there are some devices in between our sites. We cannot know the remote site down if keepalive packets cannot be sent or received from the physical or vlan interface.

Do you know any workarounds for this case?

Thanks in advance.

Walter

[tbaranski]

I'm not aware of a specific feature for VLAN interfaces (such as end-to-end keepalives for Frame Relay) that will help you here. Generally, routing protocols are used to detect and route around interfaces that lose connectivity. If you want to give more specifics about what type of failover you're trying to acheive (I'm assuming the issue here is failover if you want a VLAN interface to change state when it loses connectivity), we may be able to give more specific suggestions.

With Ethernet becoming so popular in the Metro, this is an issue that vendors and standards bodies are going to have to work on (I'm sure they are already). Cisco is slowly introducing failover-related features that help out in these types of situations (such as ping-based route tracking), but clearly there's a long way to go. Similar improvements in Ethernet/VLAN interface state tracking may be on the horizon.

[walee]

We have three Ethernet WAN links connecting the remote site to central office.The routing information between two sites is exchanged by using iBGP. Instead of IGP, static routes are set on these two routers with per-destination load sharing enabled.

I found that the per-destination load sharing is working fine when all WAN links are up and running. However, if the router at central office cannot detect the remote interface down, the packets are still sent on the faulty link.

I also tried to use some other routers with keepalive enabled, the router can quickly detect the link problem and stop forwarding packets to the faulty link.

Thanks.