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Hello

What am I supposed to do with glaring bugs? Are Juniper interested in
knowing those or don't they care?

In this case I found out that 19.1 behaves badly if you set [system
services subscriber-management overrides interfaces family inet
receive-gratuitous-arp]. The setting is supposed to enable updating the
ARP table when receiving gratuitous ARP from clients. Instead it makes
the router reply to those ARP packets, which causes the clients to
reject the address.

Packet monitor (somewhat shortened):

07:41:05.677882 bpf_flags 0x03,  In
    Juniper PCAP Flags [no-L2, In]
    -----original packet-----
    PFE proto 2 (ipv4): (tos 0x0, ttl  64, id 24111, offset 0, flags
[none], proto: UDP (17), length: 576) 0.0.0.0.bootpc >
255.255.255.255.bootps: [udp sum ok] BOOTP/DHCP, Request from
34:21:09:x:x:e1, length 548, xid 0x1b632c2a, Flags [Broadcast] (0x8000)
    -----original packet-----
    PFE proto 2 (ipv4): (tos 0x0, ttl 255, id 0, offset 0, flags
[none], proto: UDP (17), length: 319) 185.24.168.248.bootps >
255.255.255.255.bootpc: [udp sum ok] BOOTP/DHCP, Reply, length 291, xid
0x1b632c2a, Flags [Broadcast] (0x8000)
    -----original packet-----
    PFE proto 2 (ipv4): (tos 0x0, ttl  64, id 24111, offset 0, flags
[none], proto: UDP (17), length: 576) 0.0.0.0.bootpc >
255.255.255.255.bootps: [udp sum ok] BOOTP/DHCP, Request from
34:21:09:xx:xx:e1, length 548, xid 0x1b632c2a, Flags [Broadcast] (0x8000)
    -----original packet-----
    PFE proto 2 (ipv4): (tos 0x0, ttl 255, id 0, offset 0, flags
[none], proto: UDP (17), length: 319) 185.24.168.248.bootps >
255.255.255.255.bootpc: [udp sum ok] BOOTP/DHCP, Reply, length 291, xid
0x1b632c2a, Flags [Broadcast] (0x8000)
      Your-IP 212.237.x.237
        DHCP-Message Option 53, length 1: ACK
    -----original packet-----
    34:21:09:x:x:e1 > Broadcast, ethertype 802.1Q (0x8100), length
4294967292: vlan 301, p 0, ethertype 802.1Q, vlan 545, p 0, ethertype
ARP, arp who-has 212.237.x.237 tell 212.237.x.237
07:41:05.686691 bpf_flags 0x00, Out
    -----original packet-----
    e6:5d:37:84:53:17 > 34:21:09:x:x:e1, ethertype ARP (0x0806), length
4294967292: arp reply 212.237.x.237 is-at e6:5d:37:84:53:17
07:41:05.689680 bpf_flags 0x03,  In
    -----original packet-----
    PFE proto 2 (ipv4): (tos 0x0, ttl  64, id 24111, offset 0, flags
[none], proto: UDP (17), length: 576) 0.0.0.0.bootpc >
255.255.255.255.bootps: [udp sum ok] BOOTP/DHCP, Request from
34:21:09:x:x:e1, length 548, xid 0x1b632c2a, Flags [Broadcast] (0x8000)
        DHCP-Message Option 53, length 1: Decline
^C
8 packets received by filter

The part that is plain wrong is "arp reply 212.237.x.237 is-at
e6:5d:37:84:53:17". NO! 212.237.x.237 is actually at 34:21:09:x:x:e1 and
by responding to this, the router causes the client to believe something
else is using the address. Therefore the client sends Decline back to
the DHCP server.

Proxy-arp settings makes no difference at all. Doesn't matter if you
have it entirely disabled or set to proxy-arp restricted. However
disabling receive-gratuitous-arp makes the router stop doing this.

If I made a case for this I am sure they will just tell me to disable
receive-gratuitous-arp which is exactly what I did. I am just curious if
there is any way to report bugs that I will live with as is. It is still
clearly something that should get fixed.

Regards,

Baldur



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