FabricPath is a technology which combines the benefits of Routing protocols, here will be Intermediate-System-to-Intermediate-System (IS-IS), and Layer 2 Network Ethernet environments.
To list some of FabricPath advantages:
- MAC Address scalability by Conversational Learning
- No spanning-tree anymore, hurray! Each switch will have its own view of Layer 2 topology and calculates the L2 topology using SPF calculation.
- Equal cost multipath forwarding for Unicast Layer 2 traffic!
- Makes any kind of topology possible!
- Configuration/Administration is not a hassle anymore
- Loop prevention/mitigation by having a TTL field in the frames
We can refer to FabricPath as “Routing MAC Addresses” or “Layer 2 over Layer 3”, but it doesn’t mean that FabricPath ports have an IP Address! In a FabricPath topology, each device is dynamically assigned a “switch-id” via Dynamic Resource Allocation Protocol (DRAP), and L2 forwarding table is populated based on reachability to each switch-id.
Function types in FabricPath
- Leaf: This is where Classic Ethernet devices are connected to. It’s the point of “MAC to switch-id” mapping. Traffic is looked up in the L2 forwarding table and then encapsulated into a MAC-in-MAC frame whose destination switch-id is the switch which the destination host is connected to. FabricPath is only supported on Cisco Nexus 5500 with NX-OS 5.1(3)N1(1) and higher as the edge (access) device in FabricPath topology.
- Spine: Cisco Nexus 7000 is supported as the aggregation device in FabricPath topology with NX-OS 5.1(1) and higher, but only based on F1 line cards. Layer 3 forwarding could be gained by adding M1 series cards.
Continue reading “A brief introduction to FabricPath”
Downstream switches inherit timers from the root (of each VLAN)
debug spanning-tree event // root port, cost, state, TCN
- BPDUgurad blocks incoming BPDUs.
- BPDUfilter blocks outgoing BPDUs.
bpdufilter default and
bpduguard default work in conjunction with
spanning-tree guard loop is similar to UDLD, but users STP BPDU keepalive.
show spanning-tree mst [detail]
In MST, load-balancing with cost/port-priority is the same as CST, PVST.
spanning-tree mst 1 cost 1
spanning-tree mst 2 port-p 0
All switches in the L2 transit path should know about the RSPAN remote-vlan, and the interconnections should be trunk. Remember to remove pruning for RSPAN VLAN from trunks.
IPphone tags voice traffic with CoS 5.
switchport priority extended cos 1
show mls qos interface f0/1
switchport voice vlan dot1p instructs the IP-phone to apply VLAN0 and CoS 5, so both Voice & Data share the same VLAN.
switchport voice vlan automatically applies portfast.
mls qos trust device cisco–ipphone means only trust CoS if received from IP-phone which is detected by CDP.
switchport backup interface Fa0/16
switchport backup interface Fa0/16 preemption mode forced
switchport backup interface Fa0/16 preemption delay 20
Fallback Bridging is the concept of bridging non-routed protocols between SVIs or native L3 router interfaces on switches. Similar to CBR and IRB on routers.
bridge 1 protocol vlan-bridge
- PVLAN requires Transparent VTP mode.
- Whenever a task asks us to optimize a switch for memory or routing, it means “sdm prefer routing“
- Macros do not accept “interface range”!
- When filtering traffic using mac-access-list remember to allow Spanning-tree and ARP stuff!
standby use-bia : not using the vMAC
standby version 2 : Uses 126.96.36.199 for inter-router communications instead of 188.8.131.52
standby 1 ip 184.108.40.206
standby 1 priority : default is 100
standby 1 : not default
standby 1 track 1 decrement // same as standby 1 track Serial0/1/0 20
Remember to add static arp for hosts when filtering ARP in LAB exam. (