早上上班时查看网络运行情况，发现Catalyst6509出现了不少Log信息，都是关于Multicast方面的，同时也出现不少OSPF重新建立邻居关系的告警信息。下面对产生的信息做一个简单描述。
1、一个是MCAST-SP-6-GC_LIMIT_EXCEEDED，详细信息如下：
Jul 20 02:23:04: %MCAST-SP-STDBY-6-GC_LIMIT_EXCEEDED: IGMP snooping was trying to allocate more Layer 2 entries than what allowed (15488)
Jul 20 02:23:04: %MCAST-SP-6-GC_LIMIT_EXCEEDED: IGMP snooping was trying to allocate more Layer 2 entries than what allowed (15488)
在思科网站查关于MCAST-SP-6-GC_LIMIT_EXCEEDED错误信息，给出如下描述：
This error message is logged when the IGMP snooping function on the switch has created the maximum
number of allowed Layer 2 (L2) entries. The default maximum number of L2 entries that the switch can create
for multicast groups is 15,488. In later versions of Cisco IOS Software, only the hardware−installed L2
multicast entries count toward the limit. Refer to Cisco bug ID CSCdx89380 ( registered customers only) for
more details. The issue is fixed in Cisco IOS Software Release 12.1(13)E1 and later.
建议的处理办法是：
You can manually raise the L2 limit. Issue the ip igmp l2−entry−limit command.
2、另外一个是MCAST-SP-6-L2_HASH_BUCKET_COLLISION，详细信息如下：
Jul 20 02:31:14: %MCAST-SP-6-L2_HASH_BUCKET_COLLISION: Failure installing (G,C)->index: (0100.5e47.8f95,152)->0x9E8 Protocol :0 Error:3
Jul 20 02:31:30: %MCAST-SP-6-L2_HASH_BUCKET_COLLISION: Failure installing (G,C)->index: (0100.5e40.5954,152)->0x9E8 Protocol :0 Error:3
Jul 20 02:31:49: %MCAST-SP-6-L2_HASH_BUCKET_COLLISION: Failure installing (G,C)->index: (0100.5e50.6572,152)->0x9E8 Protocol :0 Error:3
Jul 20 02:31:57: %MCAST-SP-6-L2_HASH_BUCKET_COLLISION: Failure installing (G,C)->index: (0100.5e71.459a,152)->0x9E8 Protocol :0 Error:3
Jul 20 02:32:02: %MCAST-SP-6-L2_HASH_BUCKET_COLLISION: Failure installing (G,C)->index: (0100.5e17.63e5,152)->0x9E8 Protocol :0 Error:3
思科网站上给出的描述如下：
This message indicates that a Layer 2 entry was not installed in the hardware because there is not enough
space in the hash bucket. Multicast packets are flooded on the incoming VLAN because the Layer 2 entry
installation failed. When limit is exceeded, flooding occurs for additional group MACs.
建议的处理办法是：
If you do not use multicast, then you can disable IGMP snooping. Otherwise, you can increase the hash entry
limit with the use of the ip igmp snooping l2−entry−limit command.
没想到6509 Version 12.2(18)SXF16版本还有这个问题，幸好6509上未启用Multicast，所以就直接把IGMP snooping关掉了，之后经过观察6509工作正常了。