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| N6040: Inconsistent network connectivity |
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Problem:
We had a really difficult issue with one of our N series 6040 NAS controllers. One of the Vfilers would only respond to certain types of traffic from certain hosts on the network.
- Some protocols like HTTP would work. Others, like ICMP and DNS, would fail.
- Different hosts on the network would show different results, some were okay while others failed.
- Failing over to the other controller in the cluster seemed to remedy the situation.
- Other Vfilers on the same controller would exhibit different results.
- Reducing the MTU size had no effect.
- Removing the failover/partner configuration or disabling the interface on the partner controller had no effect.
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Solution:
Inspecting the routing table on the problem controller revealed an inconsistency:
N6040-B> route -s
Routing tables
Internet:
Destination Gateway Flags Refs Use Interface
default 172.29.20.1 UGS 38 6075 e0M
10.80.2/24 link#12 UC 0 0 vif1-2
10.80.2.1 0:10:db:ff:10:1 UHL 0 0 vif1-2
10.80.2.250 0:50:56:b1:22:a3 UHL 0 16136 vif1-2
10.80.2.255 ff:ff:ff:ff:ff:ff UHL 0 359 vif1-2
10.80.4/24 link#13 UC 0 0 vif1-4
10.80.4.41 0:50:56:b1:76:f0 UHL 0 90 e0M
10.80.4.42 0:50:56:b1:50:a9 UHL 0 24 e0M
10.80.4.250 0:50:56:b1:32:2e UHL 0 10652 e0M
10.80.6/24 link#14 UC 0 0 vif1-6
[snip]
Here, communication with 10.80.4.41 and 10.80.4.42 was the problem. The routing table shows that the controller has in fact chosen the wrong interface.
We simply deleted the corresponding ARP entries:
N6040-B> arp -d 10.80.4.41
10.80.4.41 (10.80.4.41) deleted
N6040-B> arp -d 10.80.4.42
10.80.4.42 (10.80.4.42) deleted
All of a sudden the communication worked as it should:
N6040-B> vfiler run vf-sikker ping 10.80.4.41
===== vf-sikker
10.80.4.41 is alive
N6040-B> vfiler run vf-sikker ping 10.80.4.42
===== vf-sikker
10.80.4.42 is alive
Checking the routing table again confirmed that an incorrect entry in the ARP table had been the cause of our problems:
N6040-B> route -s
Routing tables
Internet:
Destination Gateway Flags Refs Use Interface
default 172.29.20.1 UGS 38 6410 e0M
10.80.2/24 link#12 UC 0 0 vif1-2
10.80.2.1 0:10:db:ff:10:1 UHL 0 0 vif1-2
10.80.2.250 0:50:56:b1:22:a3 UHL 0 16203 vif1-2
10.80.2.255 ff:ff:ff:ff:ff:ff UHL 0 359 vif1-2
10.80.4/24 link#13 UC 0 0 vif1-4
10.80.4.1 0:10:db:ff:10:1 UHL 0 0 vif1-4
10.80.4.41 0:50:56:b1:76:f0 UHL 0 1 vif1-4
10.80.4.42 0:50:56:b1:50:a9 UHL 0 1 vif1-4
10.80.4.250 0:50:56:b1:32:2e UHL 0 10697 e0M
[snip]
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