Frame Processing in Junos

06.02 2024 | by massimiliano

Processing steps for transit frames with an unknow source MAC address 2) Ingress PFE performs a MAC address lookup and […]

Processing steps for transit frames with an unknow source MAC address

Frame enters ingress port and attached ingress PFE

2) Ingress PFE performs a MAC address lookup and determines source MAC is unknow

3) Ingress PFE sends header information to RE, where MAC is added or discarded (MAC limiting)

4) If RE add new source MAC address to bridge table, newly added MAC entry is sent to and programmed into all PFEs

Processing steps for transit frames with an know destination MAC address

Frame enters ingress port and attached ingress PFE

2) Ingress PFE performs a MAC address lookup and determines the egress PFE port

3) Ingress PFE forward frame to egress PFE

4) Egress PFE forwards frame out egress port toward destination; no additional lookup is needed

Processing steps for transit frames with an unknow destination MAC address

Frame enters ingress port and attached ingress PFE

2) Ingress PFE performs a MAC address lookup, determines no entry exists then replicates frame out to other PFE and all other ports in the same broadcast domain (vlan)

3) All other PFEs replicate frame and forward those frames out all egress ports in the same broadcast domain; no additional lookup is needed

Processing steps for frames destinated to the Switch’s MAC address

Frame enters ingress port and attached ingress PFE

2) Ingress PFE performs a MAC address lookup. Because the destination MAC address belongs to the switch, PFE performs a Layer 3 lookup:

Frame enters ingress port and attached ingress PFE
Ingress PFE performs a MAC address lookup. Because the destination MAC address belongs to the switch, PFE performs a Layer 3 lookup:

3) Egress PFE forwards packets out egress port toward destination. No additional lookup is needed