Description

This article describes the behavior of static arp with multicast-mac address are configured.

This issue matches PR1621901.

Symptoms

On EX and QFX5K platforms, we should configure only one static arp with multicast-mac entry per IRB interface.
If we configure more than one static arp with multicast Mac entry per IRB interface, then the packets with different destination IP having static multicast mac will always go out with any one of the multicast mac configured in the system.

[Topology]

+-----------------+      +-----------------+        +-------------------------+
|                 |      |                 |        |  Cluster 1              |
|                 |      |                 |        |  Windows Server A       |
|                 |      |              ge1+------->+  VIP:192.168.0.1        |
|                 |      |                 |        |  MAC:03:bf:c0:a8:6f:01  |
|                 |      |                 |        +-------------------------+
| Windows Client  +------+ge0      (DUT)   |
|                 |      |                 |        +-------------------------+
|                 |      |                 |        |  Cluster 2              |
|                 |      |                 |        |  Windows Server B       |
|                 |      |              ge2+------->+  VIP:192.168.0.2        |
|                 |      |                 |        |  MAC:03:bf:c0:a8:6f:02  |
+-----------------+      +-----------------+        +-------------------------+

ping from windows clinet to 192.168.0.1------------->

ping from windows clinet to 192.168.0.2------------->

 

[configuration]

# set interfaces ge-0/0/0 unit 0 family inet address 192.168.100.1/24
# set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan members 100
# set interfaces ge-0/0/2 unit 0 family ethernet-switching vlan members 100
# set interfaces irb unit 100 family inet address 192.168.0.254/24 arp 192.168.0.1 multicast-mac 03:bf:c0:a8:6f:01
# set interfaces irb unit 100 family inet address 192.168.0.254/24 arp 192.168.0.2 multicast-mac 03:bf:c0:a8:6f:02
# set vlans v100 vlan-id 100
# set vlans v100 l3-interface irb.100

When capturing traffic on the server side, the mac address are the same.


Ethernet II, Src: JuniperN_00:00:01 (c0:bf:a7:00:00:01), Dst: MS-NLB-VirtServer-Multicast_c0:a8:6f:02 (03:bf:c0:a8:6f:02)<<<<<<
Internet Protocol Version 4, Src: 192.168.100.2, Dst: 192.168.0.1
Internet Control Message Protocol

Ethernet II, Src: JuniperN_00:00:01 (c0:bf:a7:00:00:01), Dst: MS-NLB-VirtServer-Multicast_c0:a8:6f:02 (03:bf:c0:a8:6f:02)<<<<<<
Internet Protocol Version 4, Src: 192.168.100.2, Dst: 192.168.0.2
Internet Control Message Protocol

Solution

This is a product limitation
https://prsearch.juniper.net/problemreport/PR1621901

We should configure only one static arp with multicast-mac entry per IRB interface.
[configuration]

# set interfaces ge-0/0/0 unit 0 family inet address 192.168.100.1/24
# set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan members 100
# set interfaces ge-0/0/2 unit 0 family ethernet-switching vlan members 200
# set interfaces irb unit 100 family inet address 192.168.0.254/24 arp 192.168.0.1 multicast-mac 03:bf:c0:a8:6f:01
# set interfaces irb unit 200 family inet address 192.168.1.254/24 arp 192.168.1.1 multicast-mac 03:bf:c0:a8:6f:02
# set vlans v100 vlan-id 100
# set vlans v100 l3-interface irb.100
# set vlans v200 vlan-id 200
# set vlans v200 l3-interface irb.200

Modification History

2023-07-28:<First Version>
2023-12-27:<modify vlan-id>