There us a keyword like primary or preferred that tells the switch which ip address to use to source traffic on a particular interface. It doesn't quite fit the behavior I remember but it could be part of the problem. What does the routing table say?
Sent from my iPhone On Mar 9, 2011, at 10:43 AM, Chris Adams <[email protected]> wrote: > I have run into an odd issue with ARP on an EX switch that I think is a > bug in JUNOS, but I wanted to see what others thought before I tried > JTAC (maybe I'm missing something). > > I have an EX2200 switch that cannot talk to one of my recursive DNS > servers. The switch is in subnet a.b.c.0/27, while the DNS IP is in > x.y.z.0/29. The DNS IP is anycasted, and the primary server serving it > is in the same a.c.b.0/27 subnet as the switch (the DNS IP is a > secondary IP on the same interface). > > When the switch tries to reach the DNS IP, it sends the packet to the > default router. The router sends it to the server, and the server sends > an ARP request for the switch's IP. The sending IP address in the ARP > request is the DNS IP. As far as I can tell, JUNOS doesn't send a > response to the ARP request. > > I'm guessing that it isn't sending a response because the sending IP is > in a different subnet, but as far as I can tell from reading the ARP RFC > (826), that is not supposed to figure into an ARP response. > > The DNS server is Linux, and I can see Linux will respond to > out-of-subnet ARP requests. I also have an old Cisco switch in the same > subnet, and it also responds to out-of-subnet ARP requests. > > If I ping the switch from the Linux server, the ARP request goes out > with the IP in the same subnet, the switch responds, the Linux server > gets an ARP cache entry, and communication works both ways for all IPs > until the ARP cache entry expires on the Linux side. > > -- > Chris Adams <[email protected]> > Systems and Network Administrator - HiWAAY Internet Services > I don't speak for anybody but myself - that's enough trouble. > _______________________________________________ > juniper-nsp mailing list [email protected] > https://puck.nether.net/mailman/listinfo/juniper-nsp > _______________________________________________ juniper-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/juniper-nsp
