PHWinfo - Afficher un message

07/03/2006, 20h55

In article <1141752369.152458.147800@u72g2000cwu.googlegroups .com>,
mark.bergman@thales-is.com wrote:

> I have been asked to with the following network scenario, which
> gives routing problems:
>
> We have 2 Digital UNIX boxes on separate LANs (A and B), with a similar
> box acting as a gateway (G) on both LANs (with routing enabled between
> the LANs); all boxes running "routed".
> Both A and B have the appropriate side of G defined as default router.
> There is a printer on each LAN (P1 and P2), P1 is an old Phaser 840
> printer (formerly Tektronix, now Xerox), P2 is a new Phaser 8500
> printer.
>
> (view diagram in fixed-width font)
> A P1
> ___|___|____
> |
> G
> B P2 |
> ___|___|___|
>
> Machines A and B have been able to print on both P1 for some time.
> P2 is a new printer, and although B can print on P2, A cannot (cannot
> ping).
> (Swopping P1 and P2 did not , i.e. problem was with P2).
>
> I looked at the situation, and said "we need to define a route to P2
> back to A", so we setup a default gateway on P2 via G (the default
> gateway was previously 0.0.0.0), and hey presto, A can now print on P2.
>
> My questions are two (the second is the most urgent):
> 1) I am assured that P1 does not have a default gateway setup. How
> then could B print to P1? (maybe P1 can recognise that packets come
> from G, and reply there?)

Maybe G performs proxy ARP? If you run tcpdump, do you see P1 sending
ARP queries for B's address, and G responding to them?

> 2) The complication to the above picture is that in fact there are two
> gateways (G1 and G2), acting as Master/Standby. I think they just rely
> on RIP to route between the 2 LANs, i.e. if G1 is down, traffic routes
> via G2. How do I get P2 to route to A if I cannot have a fixed Default
> Gateway?

If G1 and G2 are Cisco, enable HSRP. If not, see if there's a VRRP
implementation for them.

--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

07/03/2006, 20h55	#2
Barry Margolin Messages: n/a Hébergeur:	Re: Routing from printer through gateway In article <1141752369.152458.147800@u72g2000cwu.googlegroups .com>, mark.bergman@thales-is.com wrote: > I have been asked to with the following network scenario, which > gives routing problems: > > We have 2 Digital UNIX boxes on separate LANs (A and B), with a similar > box acting as a gateway (G) on both LANs (with routing enabled between > the LANs); all boxes running "routed". > Both A and B have the appropriate side of G defined as default router. > There is a printer on each LAN (P1 and P2), P1 is an old Phaser 840 > printer (formerly Tektronix, now Xerox), P2 is a new Phaser 8500 > printer. > > (view diagram in fixed-width font) > A P1 > ___\|___\|____ > \| > G > B P2 \| > ___\|___\|___\| > > Machines A and B have been able to print on both P1 for some time. > P2 is a new printer, and although B can print on P2, A cannot (cannot > ping). > (Swopping P1 and P2 did not , i.e. problem was with P2). > > I looked at the situation, and said "we need to define a route to P2 > back to A", so we setup a default gateway on P2 via G (the default > gateway was previously 0.0.0.0), and hey presto, A can now print on P2. > > My questions are two (the second is the most urgent): > 1) I am assured that P1 does not have a default gateway setup. How > then could B print to P1? (maybe P1 can recognise that packets come > from G, and reply there?) Maybe G performs proxy ARP? If you run tcpdump, do you see P1 sending ARP queries for B's address, and G responding to them? > 2) The complication to the above picture is that in fact there are two > gateways (G1 and G2), acting as Master/Standby. I think they just rely > on RIP to route between the 2 LANs, i.e. if G1 is down, traffic routes > via G2. How do I get P2 to route to A if I cannot have a fixed Default > Gateway? If G1 and G2 are Cisco, enable HSRP. If not, see if there's a VRRP implementation for them. -- Barry Margolin, barmar@alum.mit.edu Arlington, MA * PLEASE post questions in newsgroups, not directly to me * * PLEASE don't copy me on replies, I'll read them in the group *