At 08:15 AM 3/14/01, John Neiberger wrote:
>I don't mind the redirects, I just want to know by
>what mechanism the hosts switch back to using the original default
>gateway. Is there a timeout of some sort? Does it require a reboot?
It does not require a reboot, but the exact behavior would depend on the OS
and TCP/IP stack. My experience studying Windows and Macs shows that hosts
revert to their default gateway very quickly. In fact some versions of
Windows ignore ICMP redirects entirely. Others go back to the default when
an application is restarted. Others when the TCP/IP stack is restarted.
Some revert to the default gateway with every session, which means every
click on a URL with TCP/HTTP. Can you study your own network with a
sniffer? That would be the best way to tell.
Priscilla
> I
>haven't read anywhere how things are adjusted back to normal after the
>fact.
>
>Thanks,
>John
>
> >>> "Paul Werner" <[EMAIL PROTECTED]> 3/13/01 11:47:04 PM >>>
>A couple of thoughts here. This is clearly the territory that
>HSRP was designed to address, namely failure of a primary
>gateway and assumption of the backup gateway while the primary
>is down. First, you may want to take a peek at this article
>(watch wrap):
>
>http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/
>121newft/121t/121t3/dt_hsrpi.htm
>
>On the other hand, you could block any ICMP redirects with a
>simple access list(which creates other problems). It seems
>that it might be more beneficial to get hardware that will
>ultimately do the job you are trying to do via HSRP.
>
>Regarding the issue of HSRP support for CBOS based platforms
>(600 series Cisco devices) you are correct, the support is not
>there. OTOH, I don't know if your flavor of DSL will fit the
>profile, but have you considered using a 1720-ADSL router? It
>*appears* that with the WIC-1ADSL installed, support is there
>for HSRP. 1720's go new in the $700-$800 range. the WIC-
>1ADSL can be had for approximately $500 new. Of course, you
>could probably get them both used for a lot less.
>
>HTH,
>
>Paul Werner
>
>
> > When a host receives an ICMP redirect, it's my understanding
>that it
> > places a host route in the routing table for that
>destination. How long
> > does that route typically stay in the table? If the route is
>being
> > used, would it stay there indefinitely? Here's why I ask...
> >
> > We have a 2620 and a 675 attached to the same remote LAN.
>The 675 is
> > there in case the frame relay circuit to the building goes
>down.
> > Because they are on the same subnet, I noticed that the 2620
>began
> > sending redirects to the users. If the circuit were to come
>back up,
> > how would the hosts know to start using their original
>default gateway?
> >
> > The 675 and 2620 are not speaking a routing protocol to each
>other,
> > we're using static routes only. Proxy ARP isn't an option
>because we
> > want the PCs to always use the frame relay T1 if it is
>available. HSRP
> > is not an option because the 675 does not support it.
>
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