Good to know.

Slightly OT, but why would they have ARP cache timeouts of four hours?
 What benefit do you get with such high cache times as opposed to the
obvious support calls you will get when equipment is swapped around?

-A


On Sat, May 10, 2014 at 7:55 PM, Moshe Katz <[email protected]> wrote:

> On Fri, May 9, 2014 at 10:56 PM, Aaron C. de Bruyn <[email protected]>wrote:
>
>> Spent about an hour beating my head against the wall with this issue,
>> hopefully this will save others some time.
>>
>> We had a stand-alone pfSense router.
>> We just purchased two machines from ixsystems and were preparing them to
>> be a failover pair of pfSense routers and then decommission the smaller
>> older box.
>>
>> While we were installing the new servers, the HDD in the old firewall
>> died.
>>
>> We figured we would just get the two new boxes up.
>>
>> Plugged them into the Comcast modem and configured everything.
>>
>> Comcast assigned us a /28 a while back and we were using a handful of IPs
>> to access various internal services over HTTPS.
>>
>> The /28 looked roughly like:
>> .1 - router1
>> .2 - router2
>> .3 - exchange (CARP)
>> .4 - remote (CARP)
>> .5 - VPN (CARP)
>> .6 - spamfilter (physical machine)
>> ...etc
>>
>> After everything was configured, I had someone test remotely that they
>> could access the interface for router1 and router2 remotely.
>>
>> I then went home to finish up a few config details remotely.
>>
>> When I got home, I found I could access router1 and router2 as well as
>> the physical spam filter, but I couldn't access any of the HTTPS services
>> on the CARP IPs.
>>
>> I checked my NAT rules about 100 times, looked through firewall logs, and
>> found nothing.
>>
>> Finally I connected in to the spam filter (linux box) and ran 'openssl
>> s_client -connect exchange.example.tld:4433' and noticed it worked
>> perfectly from a machine on the same WAN segment.   ...but not remotely.
>>
>> I called Comcast and had them remotely reboot the modem.  Everything
>> immediately came up and started working perfectly.
>>
>> Hopefully this will save someone time.  Reboot the brain-damaged Netgear
>> CPE after swapping hardware around.
>>
>> -A
>>
>
> Hi Aaron,
>
> Most cable modems I have worked with in the US (on Comcast, Optimum, and
> RCN) all do ARP caching, so you need to reboot them when you change the
> connected device (or you need to clone the old device's MAC address).
>
> Actually though, working with DSL is worse.  Verizon DSL does ARP caching
> in the Central Office for up to four hours.  I have found that replacing
> equipment hooked up to Verison DSL, it is best to already be on the phone
> with Verizon support to have them manually clear the cache.  At least
> rebooting the cable modem is something you can do yourself.
>
> Moshe
>
> --
> Moshe Katz
> -- [email protected]
> -- +1(301)867-3732
>
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