Duplicate IP Detected, Gratuitous ARP

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  • Updated 10 months ago
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I am trying to move our Polycom unit to its own VLAN to try and isolate/eliminate dropped packets.  I changed the static IP address, subnet, and gateway on the Polycom out of the range of the existing Admin network.

I created the VLAN and tried to mimic what was already existing on the switch in terms of IP addresses and routes.  I am able to navigate to the web gui of the Polycom and connect to make calls but I must have done something incorrectly as I am getting numerous Gratuitous ARP entries in Wireshark and the dropped packets remain.

Any help in troubleshooting this issues would be appreciated.

Here are some configuration outputs:

EXOS
show  port 47 info detail
VLAN cfg:
Name: DistanceLearning, Internal Tag = 170, MAC-limit = No-limit, Virtual router: VR-Default

show  port 48 info detail
VLAN cfg:
                 Name: DistanceLearning, Internal Tag = 170, MAC-limit = No-limit, Virtual router: VR-Default

show vlan
Admin           4091 172.16.0.254   /21  -f----------------------- ANY    118/182 VR-Default
Default         1    --------------------------------------------- ANY    0 /0   VR-Default
DistanceLearning 170  172.16.170.1   /24  ------------------------- ANY    2/2   VR-Default
Mgmt            4095 --------------------------------------------- ANY    0 /1   VR-Mgmt

show config
create vlan "DistanceLearning"
configure vlan DistanceLearning tag 170
configure vlan DistanceLearning add ports 2:47-48 untagged
configure iproute add default 172.16.0.1

show iproute
Ori  Destination        Gateway         Mtr  Flags         VLAN       Duration
#s   Default Route      172.16.0.1      1    UG---S-um--f- Admin      24d:15h:18m:9s
#d   172.16.0.0/21      172.16.0.254    1    U------um--f- Admin      24d:15h:18m:22s
#d   172.16.170.0/24    172.16.170.1    1    U------um--f- DistanceLearning 1d:19h:31m:5s


Wireshark
3.893275000 Watchgua_d7:62:b8 MS-NLB-PhysServer-04_96:52:6b:7a ARP 60 Gratuitous ARP for 172.16.170.1 (Reply) (duplicate use of 172.16.170.1 detected!)
  • Address Resolution Protocol (request/gratuitous ARP)
  • Sender MAC address: MS-NLB-PhysServer-04_96:52:6b:7a (02:04:96:52:6b:7a)
  • Sender IP address: 172.16.170.1 (172.16.170.1)
  • Target MAC address: 00:00:00_00:00:00 (00:00:00:00:00:00)
  • Target IP address: 172.16.170.1 (172.16.170.1)

Firebox ARP
172.16.0.254     0x1         0x2         02:04:96:52:6b:7a     *        eth1
172.16.170.1     0x1         0x2         02:04:96:52:6b:7a     *        eth2


Diagram
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John Cook

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  • confused

Posted 10 months ago

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Eric Burke

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Not sure if I'm reading it wrong, but it looks like you have the same IP address defined at a virtual IP in the same VLAN (meaning the switch has .1 and the firewall has .1)...
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John Cook

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Indeed, you are correct.  Thanks for taking the time to review this issue.
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Eric Burke

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Any time!