Static arp entry cat 4500, multicast routing

Unanswered Question
Jul 21st, 2008

Hello all i have a 4500 with a static arp entry for a virtual server. all has been working fine for 6 months. config below.

arp 03bf.5ef0.8185 ARPA alias

i have now enabled multicast routing on the 4500 and added a pim statement to the vlan interface.

This has stopped me from pinging the virtual server from the vlan the server is sat in. I can ping the virtual server from other vlans. When i remove the pim statement all works fine ?

confused why enabling pim would cause issue with the static arp entry.

I have this problem too.
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Giuseppe Larosa Fri, 07/25/2008 - 19:54

Hello Dave,

I think you have associated an IPv4 unicast IP address to a multicast MAC address 03bf.5ef0.8185 (not a multicast MAC address for IPv4 multicast).

A multicast MAC address is characterized by having the least significant bit (rightmost bit) of the most significant byte ( leftmost byte) set to 1.

This is the I/G bit.

So I suppose that when you enable ip pim on the Vlan some form of additional control is performed.

See the following link for the MAC address format

Layer 2 Multicast Addressing

The IEEE 802.2 specification makes provisions for the transmission of broadcast and multicast packets. As shown in Figure 2, Bit 0 of Octet 0 in an IEEE MAC address indicates whether the destination address is a broadcast/multicast address or a unicast address.

Hope to help


littledavewhite Thu, 07/31/2008 - 10:28

thanks for the post i will have a look at the configuration. and see what happens. I got the mac address from the server guys so maybe a mistake.




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