Hello,

We have a F760 running Data Ontap 6.4.5. (Pretty old stuff, I know.) The filer has six network interfaces, each one connected to a different network.

Recently we started experimenting with a Linux Fedora Core 6 machine. When we try to mount some directory at the filer from this machine, almost always the process hang. A very few times the process succeeds.

Investigating the issue using tcpdump I discovered that in the process of mouting, when the filer's portmapper answers to the Linux box, sometimes its answers come from a different network interface and the Linux box doesn't like that.

See below the history of an unsuccessful mount. The Linux box (10.202.40.66) tries to mount a directory from filer (10.202.48.109) with the following command and hangs until I kill it:

mount filer:/vol/vol0/unix/config /mnt

Note that on packet 111 the linux box sends a UDP packet to the filer's portmapper asking for the port number of the MOUNT service. The filer responds with packet 113, which comes from another of its interfaces (10.202.40.23). This response is rejected by the linux box with the ICMP packet number 114.

If I try to mount specifying the interface 10.202.40.23, which is in the same network as the client, the mount succeeds. It seems that the portmapper response always tries to go back through the interface in the same network as the client.

The problem is that we have some linux clients on networks on which there is no filer interface connected. In these cases it seems to be anyone's guess through which interface the portmapper response will come.

We looked for differences in the TCP stack from Fedora Core 5 to 6, because until Core 5 this problem didn't arise, but we couldn't find anything relevant. Since the filer works ok with other Linux and Solaris machines, it seems that something must have been changed in the Linux kernel that made it more strict.

We suspected of some firewall rules, but there is no iptables rules configured in the linux box.

Has anybody seen this before? Any clue?

Thank you.

Gustavo.

---------------------------------------------------------------------- No. Time Source Destination Protocol Info 94 1.036676 10.202.40.66 10.202.48.109 TCP 33614 > sunrpc [SYN] Seq=0 Len=0 MSS=1460 TSV=16336999 TSER=0 WS=6 95 1.038301 10.202.48.109 10.202.40.66 TCP sunrpc > 33614 [SYN, ACK] Seq=0 Ack=1 Win=8760 Len=0 MSS=1460 WS=0 TSV=242744087 TSER=16336999 96 1.038319 10.202.40.66 10.202.48.109 TCP 33614 > sunrpc [ACK] Seq=1 Ack=1 Win=5888 Len=0 TSV=16336999 TSER=242744087 97 1.038385 10.202.40.66 10.202.48.109 Portmap V2 GETPORT Call (Reply In 98) NFS(100003) V:3 TCP 98 1.039907 10.202.48.109 10.202.40.66 Portmap V2 GETPORT Reply (Call In 97) Port:2049 99 1.039914 10.202.40.66 10.202.48.109 TCP 33614 > sunrpc [ACK] Seq=61 Ack=33 Win=5888 Len=0 TSV=16337000 TSER=242744087 100 1.039939 10.202.40.66 10.202.48.109 TCP 33614 > sunrpc [FIN, ACK] Seq=61 Ack=33 Win=5888 Len=0 TSV=16337000 TSER=242744087 101 1.039966 10.202.40.66 10.202.48.109 TCP 34612 > nfs [SYN] Seq=0 Len=0 MSS=1460 TSV=16337000 TSER=0 WS=6 102 1.040592 10.202.48.109 10.202.40.66 TCP sunrpc > 33614 [ACK] Seq=33 Ack=62 Win=8760 Len=0 TSV=242744087 TSER=16337000 103 1.040669 10.202.48.109 10.202.40.66 TCP nfs > 34612 [SYN, ACK] Seq=0 Ack=1 Win=26280 Len=0 MSS=1460 WS=0 TSV=242744087 TSER=16337000 104 1.040677 10.202.40.66 10.202.48.109 TCP 34612 > nfs [ACK] Seq=1 Ack=1 Win=5888 Len=0 TSV=16337000 TSER=242744087 105 1.040722 10.202.40.66 10.202.48.109 TCP [TCP segment of a reassembled PDU] 106 1.040849 10.202.48.109 10.202.40.66 TCP sunrpc > 33614 [FIN, ACK] Seq=33 Ack=62 Win=8760 Len=0 TSV=242744087 TSER=16337000 107 1.040856 10.202.40.66 10.202.48.109 TCP 33614 > sunrpc [ACK] Seq=62 Ack=34 Win=5888 Len=0 TSV=16337000 TSER=242744087 108 1.041776 10.202.48.109 10.202.40.66 NFS V3 NULL Reply (Call In 105) 109 1.041782 10.202.40.66 10.202.48.109 TCP 34612 > nfs [ACK] Seq=45 Ack=33 Win=5888 Len=0 TSV=16337000 TSER=242744087 110 1.041801 10.202.40.66 10.202.48.109 TCP 34612 > nfs [FIN, ACK] Seq=45 Ack=33 Win=5888 Len=0 TSV=16337000 TSER=242744087 111 1.041847 10.202.40.66 10.202.48.109 Portmap V2 GETPORT Call (Reply In 113) MOUNT(100005) V:3 UDP 112 1.042834 10.202.48.109 10.202.40.66 TCP nfs > 34612 [ACK] Seq=33 Ack=46 Win=26280 Len=0 TSV=242744087 TSER=16337000 113 1.042842 10.202.40.23 10.202.40.66 Portmap V2 GETPORT Reply (Call In 111) Port:4046 114 1.042851 10.202.40.66 10.202.40.23 ICMP Destination unreachable (Port unreachable) 115 1.042854 10.202.48.109 10.202.40.66 TCP nfs > 34612 [FIN, ACK] Seq=33 Ack=46 Win=26280 Len=0 TSV=242744087 TSER=16337000 116 1.042857 10.202.40.66 10.202.48.109 TCP 34612 > nfs [ACK] Seq=46 Ack=34 Win=5888 Len=0 TSV=16337000 TSER=242744087