This article describes a scenario where aliasing label value of 0 can be seen.
In an EVPN multi-homing setup, configuring same RD (Route-Distinguisher) on the remote PE's can lead to '0' being installed as Aliasing label in the remote PE. This is an invalid configuration. Distinct RD value must be configured on the multi-homing PE's. This could lead to traffic being sent using MAC label instead of Aliasing label, which can lead to packet drop on the remote PE as it is expecting the traffic to being sent with Aliasing label.
Below is a sample EVPN setup with PE2 and PE3 in active-active multi-homing setup. PE1 is single homed. If the same RD value is misconfigured on both PE2 and PE3, it can lead to programming a aliasing label of '0' on PE1.
+----------+ +------------+
| | | |
| | | PE2 +--------+
| +-------------------------------+ |
| | | |
| | +------|------+
| PE1 |
+---------+ |
| |
| | +-------------+
| | | |
| | | PE3 +--------+
| +-------------------------------+ |
| | | |
| | +-------------+
+----------+
Sample config and output:
PE2
routing-instances {
EVPN {
instance-type virtual-switch;
inactive: interface ge-5/0/0.0;
interface ge-5/0/1.0;
interface ge-5/1/9.0;
route-distinguisher 1:2;
vrf-target target:1:2;
protocols {
evpn {
traceoptions {
file EVPN.log size 10m;
flag all;
}
extended-vlan-list 1;
}
}
bridge-domains {
BD-1 {
domain-type bridge;
vlan-id 1;
routing-interface irb.0;
}
BD-2 {
domain-type bridge;
vlan-id 2;
}
}
}
}
PE3
routing-instances {
EVPN {
instance-type evpn;
vlan-id 1;
inactive: interface ge-5/1/0.0;
interface ge-5/1/1.0;
interface ge-5/1/9.0;
routing-interface irb.0;
route-distinguisher 1:2;
vrf-target target:1:2;
protocols {
evpn {
traceoptions {
file evpn.log size 10m;
flag all;
}
}
}
}
VRF {
instance-type vrf;
interface irb.0;
route-distinguisher 1:5;
vrf-target target:1:2;
}
}
user@PE1> show evpn instance extensive
Instance: EVPN
Route Distinguisher: 1:2
VLAN ID: 1
Per-instance MAC route label: 299776
Per-instance multicast route label: 299792
MAC database status Local Remote
Total MAC addresses: 0 4294967295
Default gateway MAC addresses: 1 3
Number of local interfaces: 2 (1 up)
Interface name ESI Mode Status
ge-5/1/1.0 01:02:03:04:05:06:07:08:09:00 all-active Up
ge-5/1/9.0 00:00:00:00:00:00:00:00:00:00 single-homed Down
Number of IRB interfaces: 1 (1 up)
Interface name Status L3 context
irb.0 Up VRF
Number of neighbors: 2
10.255.32.32
Received routes
MAC address advertisement: 1
MAC+IP address advertisement: 1
Inclusive multicast: 1
Ethernet auto-discovery: 1
10.255.32.59
Received routes
MAC address advertisement: 1
MAC+IP address advertisement: 1
Inclusive multicast: 1
Ethernet auto-discovery: 0
Number of ethernet segments: 1
ESI: 01:02:03:04:05:06:07:08:09:00
Local interface: ge-5/1/1.0, Status: Up/Forwarding
Number of remote PEs connected: 1
Remote PE MAC label Aliasing label Mode <<< THIS IS WRONG
10.255.32.32 0 0 all-active
Designated forwarder: 10.255.32.38
Backup forwarder: 10.255.32.32
Advertised MAC label: 299840
Advertised aliasing label: 299840
Advertised split horizon label: 299856
Instance: __default_evpn__
Route Distinguisher: 10.255.32.38:0
VLAN ID: 0
Per-instance MAC route label: 299808
Per-instance multicast route label: 299824
MAC database status Local Remote
Total MAC addresses: 0 0
Default gateway MAC addresses: 0 0
Number of local interfaces: 0 (0 up)
Number of IRB interfaces: 0 (0 up)
Number of neighbors: 1
10.255.32.32
Received routes
Ethernet auto-discovery: 0
Ethernet Segment: 1
Number of ethernet segments: 0