x440-24p - IPMC Group Table Entries - full

[Michal_Rz]

Hello,
I have problem that apears here kinda often, but not a single one that matches mine.

In logs of X440-24p running on 16.1.3.6 i see from some time:
IPv4 multicast entry not added. Hardware Group Table full.

I have only few vlans on it, and it works as AP access switch. Nothing special.

Some commands that I think might be interesting.
debug hal show ipv4Mc

Total IPMC Cache Entries : 2(IPv4 : 2, IPv6 :0)
Total IPMC Caches with No Group Index : 1(IPv4 : 1, IPv6 :0)
L2 Mode Caches with No Group Index : 0(IPv4 : 0, IPv6 :0)
L3 Mode Caches with No Group Index : 1(IPv4 : 1, IPv6 :0)
IPMC Group Table Entries In-use : 64
IPMC Group Table Entries Max : 64
L2MC Group Table Entries In-use : 0
L2MC Group Table Entries Max : 0
IPMC Forwarding Mode : 1

vrId 2 G=239.255.255.250 S=255.255.255.255 Vid 394 : (HW IPMC -1 l3hash 0 hit 0)
vrId 2 G=239.255.255.250 S=10.160.35.30 Vid 394 : (HW IPMC -1 l3hash 0 hit 0)
-> Vid 394
-> 1

show iproute reserved-entries statistics
|-----In HW Route Table-----| |-------In HW L3 Hash Table------|
# Used Routes # IPv4 Hosts IPv4 IPv4 IPv6 IPv4 IPv6
Slot Type IPv4 IPv6 Local Remote Local Rem. Local MCast MCast
---- --------------- ------- ------ ------ ------ ----- ----- ----- ------ ------
1 X440-24p 0 0 0 0 0 0 0 0 0

show forwarding configuration

L2 and L3 Forwarding table hash algorithm:
Configured hash algorithm: crc32
Current hash algorithm: crc32
L3 Dual-Hash configuration:
Configured setting: on
Current setting: on
Dual-Hash Recursion Level: 3
Hash criteria for IP unicast traffic for L2 load sharing and ECMP route sharing
Sharing criteria: L3_L4
IP multicast:
Group Table Compression: on
Local Network Forwarding: slow-path
Lookup-Key: (*,GroupIP,VlanId)
Switch Settings:
Switching mode: store-and-forward
L2 Protocol:
Fast convergence: on
Fabric Flow Control:
Fabric Flow Control: auto

Any ideas what might fill the IPMC Group Table to the maximum? Or its not the issue?

[Michal_Rz]

FYI I have disabled acl for tests. Also switch rebooted second time after test command: clear ipmc fdb group 239.255.255.250. Dont know why.

By the way my SIEM told me that I have loged this issue 3200 times in last year on about 30 switches, 900times on this one Im talking about.

And it shows right now that:
debug hal show ipv4Mc

Total IPMC Cache Entries : 8(IPv4 : 8, IPv6 :0)
Total IPMC Caches with No Group Index : 0(IPv4 : 0, IPv6 :0)
L2 Mode Caches with No Group Index : 0(IPv4 : 0, IPv6 :0)
L3 Mode Caches with No Group Index : 0(IPv4 : 0, IPv6 :0)
IPMC Group Table Entries In-use : 5
IPMC Group Table Entries Max : 5
L2MC Group Table Entries In-use : 0
L2MC Group Table Entries Max : 0
IPMC Forwarding Mode : 1

vrId 2 G=224.0.0.251 S=255.255.255.255 Vid 392 : (HW IPMC 2 l3hash 0 hit 0)
vrId 2 G=224.0.0.251 S=255.255.255.255 Vid 362 : (HW IPMC 1 l3hash 0 hit 0)
vrId 2 G=224.0.0.251 S=xxx.xxx.xxx.xxx(public IP) Vid 362 : (HW IPMC -1 l3hash 0 hit 0)
-> Vid 362
-> 3 4 5 6 7 8 9 10 11 12
13 14 15 16 17 18 19 20 1
vrId 2 G=224.0.0.251 S=10.160.3.112 Vid 392 : (HW IPMC -1 l3hash 0 hit 0)
-> Vid 392
-> 3 4 5 6 7 8 9 10 11 12
13 14 15 16 17 18 19 20 1
vrId 2 G=239.255.255.250 S=255.255.255.255 Vid 394 : (HW IPMC 3 l3hash 0 hit 0)
vrId 2 G=239.255.255.250 S=10.160.39.15 Vid 394 : (HW IPMC -1 l3hash 0 hit 0)
-> Vid 394
-> 1
But today its lazy day, so almost no one are online.

Happy new year 🙂

[Bill_Stritzinge]

Michal,

The easiest way to solve this is to set the following:
"configure igmp snooping forwarding-mode group-vlan"

- - -> reduces igmp entries – by default it was source,group,vlan – which will give you more IPMC entries

This is non-evasive and should solve the problem.

Bill

[Michal_Rz]

Thats right, changed that some time ago.

[OscarK]

Hello Bill, this switch is already in group-vlan mode, you can see that in show forwarding config where it is shown as (*,groupIP,vlanID).

[Alexandr_P]

Hello!

You have to understand that DENY and DENY-CPU - it's different actions.
deny-cpu—Prevents packets that are copied or switched to the CPU from reaching the CPU. The data-plane forwarding of these packets is unaffected.

Thank you!