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
