Unable to set a Static Multicast ARP on the SecureStack router

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  • Updated 5 years ago
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Article ID: 12596 

Products
SecureStack C3, SecureStack C2
SecureStack B3 

Changes
Trying to configure a static multicast ARP (i.e. 'arp <IP_address> <MAC_address>') on the router. 
One reason is to use virtual MAC address 03bf-c0xx-xx-xx for Microsoft Server Load Balancing. 
Another reason is to allow the 'set mac multicast' command to operate through a routed interface (5708). 

Symptoms
The router mode command is rejected, with error message "Unable to perform ARP operation". 

For example:
C3(su)->router
C3(su)->router>enable
C3(su)->router#config
Enter configuration commands:
C3(su)->router(Config)#arp 10.20.17.77 03bf.c0a8.114d
Error: Unable to perform ARP operation
C3(su)->router(Config)#exit
C3(su)->router#exit
C3(su)->router>exit
C3(su)->
This command in router mode supports the use of unicast MAC addresses, but not multicast MAC addresses. 
This command in switch mode supports the use of unicast or multicast MAC addresses. 

Solution
Functions as Designed (FAD). 

Note: Beginning around the C5/C3/B5/B3 v6.42.01.0046 release, the router-mode multicast ARP command can be successfully entered but does not function as expected. IP-matching traffic will not be hardware-forwarded to the configured MAC address but will instead be CPU-forwarded to all ports in the destination VLAN - and in consequence will also be rate-limited to 64 packets per second (pps). Due to this functional inefficiency, router-mode multicast ARP is still not considered to be supported.
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Posted 5 years ago

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