Wired and Wi-Fi network hopping and DHCP Server default gateway route metric increases

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Wired and Wi-Fi network hopping and DHCP Server default gateway route metric increases

L1 Bithead

At my remote offices, I have users that want to leave WiFi and wired on at the same time.

 

I have redundant PA-220's that serve as my local router and DHCP server for both wired and Wi-Fi.

 

The wired and wireless connections are in different networks (/24's) and thus have different default routes.  Some users have troubles with weird applications that (supposedly) want to flip back and forth between default routes from time to time, and thus cause strange behavior.  In order to mitigate this risk at HQ, I use Windows DHCP Server (not by choice...) and use option 3 (https://supportforums.cisco.com/t5/lan-switching-and-routing/dhcp-scope-option-metric-base/td-p/1631...) to increase the metric on the default route for the wireless network.

 

I would like to do the same on my wireless network at remote sites to ensure that there's never a question of which default route to use when a user is connected to the wired network.

 

Does anyone else have this or a similar/related problem?

 

What are other ways to get around this issue?

 

4 REPLIES 4

Cyber Elite
Cyber Elite

@jfreeland,

If you are using option 3 on your Windows DHCP server you could push the same option via the Palo Alto DHCP server in the remote offices. 

Thanks for the quick response!

 

Technically I could server DHCP with Option 3 from my Windows DHCP Server, but I really don't want to serve DHCP over WAN.  I've had enough outages over the years that I've decided to keep what I can locally to remove any dependencies for base services.

 

I did some testing myself and I reached out to Palo Alto support, and I could not get DHCP option 3 to work from the Palo Alto DHCP Server.  It's not entirely clear to me how Windows supports this, but none of the options I used had any impact on metrics handed out to clients from the Palo Alto DHCP server.

L2 Linker

Think you may be trying to solve this from the wrong piece of infrastructure.  I'd suggest focusing on the client side and narrowing down why the ethernet connection isn't preferred to the WLAN connection without any metric adjustments.  When the routes look like they flip back and forth, do you see their ethernet dropping connection in the event logs on the laptop or on your switches? 

 

This might not fit your particular situation, but we only use HP laptops which have an option in the BIOS for LAN/WLAN switching which disabled wireless automatically when an ethernet connection is detected.  I'm pretty sure our Help Desk people set this on all of our laptops to avoid this exact issue.

@carlebert,

Suprisngly HP and Dell are some of the only laptops that I know off in the enterprise segment that do this. Lenovo for whatever reason will allow both entries, and while it prioritizes ethernet it isn't uncommon to see them using the WLAN connection. 

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