STP, UplinkFast, and Bridge Groups
Hi guys,
Calling in the experts because I need some help on a topology I'm working on. First, let me share the lab.
Allright, so the fa1/0 connection between SW01 and SW02 is a VLAN trunk. fa1/1 on both switches is configured as an access port in VLAN 10. SW02 is configured as the STP root bridge for VLAN 10 (spanning-tree vlan 10 root primary) and SW01 is the secondary (that doesn't really matter here). Here comes the magic.
R1 on the bottom is configured as a bridge, basically bridging fa0/0 and fa0/1. So, to prevent a switching loop, STP puts the path towards SW01 in BLK mode. So far, so good. However, an issue occurs when I shutdown fa0/1 (the current FWD / Root port) on R1, to do a failover towards fa0/0. The connectivity is restored after a 20 seconds by tweaking the STP timers (max-age and forward delay to 6 and 4 seconds respectively).
However, I'd like to see that those 20 seconds could be brought down even further. In doing so, I thought of 2 options:
Enabling RSTP on the bridge router (R1)
Very little to find about RSTP here. ieee refers to 802.1D (classic spanning-tree), which is what is running now.
Enabling UplinkFast
Well, if RSTP can't do the job, perhaps uplinkfast can.
So far so good you'd say. When I disable fa0/1 on R1, the router seems to go through the normal STP states and does not go directly into FWD'ing mode:
Very little UplinkFast to see here. Is it some kind of unwritten rule that bridge-groups and uplinkfast do not play well together?
Calling on you guys, experts
Tell me what I'm missing here.
R1 config
Calling in the experts because I need some help on a topology I'm working on. First, let me share the lab.
Allright, so the fa1/0 connection between SW01 and SW02 is a VLAN trunk. fa1/1 on both switches is configured as an access port in VLAN 10. SW02 is configured as the STP root bridge for VLAN 10 (spanning-tree vlan 10 root primary) and SW01 is the secondary (that doesn't really matter here). Here comes the magic.
R1 on the bottom is configured as a bridge, basically bridging fa0/0 and fa0/1. So, to prevent a switching loop, STP puts the path towards SW01 in BLK mode. So far, so good. However, an issue occurs when I shutdown fa0/1 (the current FWD / Root port) on R1, to do a failover towards fa0/0. The connectivity is restored after a 20 seconds by tweaking the STP timers (max-age and forward delay to 6 and 4 seconds respectively).
However, I'd like to see that those 20 seconds could be brought down even further. In doing so, I thought of 2 options:
Enabling RSTP on the bridge router (R1)
R1(config)#bridge 1 protocol ? dec DEC protocol ibm IBM protocol ieee IEEE 802.1 protocol vlan-bridge vlan-bridge protocol
Very little to find about RSTP here. ieee refers to 802.1D (classic spanning-tree), which is what is running now.
Enabling UplinkFast
Well, if RSTP can't do the job, perhaps uplinkfast can.
R1#sh spanning-tree uplinkfast UplinkFast is enabled Station update rate set to 150 packets/sec. UplinkFast statistics ----------------------- Number of transitions via uplinkFast (all VLANs) : 0 Number of proxy multicast addresses transmitted (all VLANs) : 0 Name Interface List -------------------- ------------------------------------ Bridge group 1 Fa0/1(fwd), Fa0/0
So far so good you'd say. When I disable fa0/1 on R1, the router seems to go through the normal STP states and does not go directly into FWD'ing mode:
*Mar 1 02:36:41.091: STP: Bridge group 1 Fa0/1 -> blocking *Mar 1 02:36:41.091: STP: Bridge group 1 new root port Fa0/0, cost 119 *Mar 1 02:36:41.091: STP: Bridge group 1 Fa0/0 -> listening *Mar 1 02:36:43.083: %LINK-5-CHANGED: Interface FastEthernet0/1, changed state to administratively down *Mar 1 02:36:43.087: %LINK-3-UPDOWN: Interface BVI1, changed state to down *Mar 1 02:36:43.091: STP: Bridge group 1 sent Topology Change Notice on Fa0/0 *Mar 1 02:36:44.083: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down *Mar 1 02:36:44.087: %LINEPROTO-5-UPDOWN: Line protocol on Interface BVI1, changed state to down *Mar 1 02:36:45.091: STP: Bridge group 1 Fa0/0 -> learning *Mar 1 02:36:48.835: %LINK-3-UPDOWN: Interface BVI1, changed state to up *Mar 1 02:36:49.091: STP: Bridge group 1 sent Topology Change Notice on Fa0/0 *Mar 1 02:36:49.091: STP: Bridge group 1 Fa0/0 -> forwarding *Mar 1 02:36:49.835: %LINEPROTO-5-UPDOWN: Line protocol on Interface BVI1, changed state to up
Very little UplinkFast to see here. Is it some kind of unwritten rule that bridge-groups and uplinkfast do not play well together?
Calling on you guys, experts
Tell me what I'm missing here.R1 config
R1#sh run Building configuration... Current configuration : 1128 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname R1 ! boot-start-marker boot-end-marker ! ! no aaa new-model memory-size iomem 5 no ip icmp rate-limit unreachable ip cef ! ! no ip domain lookup ! multilink bundle-name authenticated ! spanning-tree uplinkfast archive log config hidekeys ! bridge irb ! interface FastEthernet0/0 no ip address duplex auto speed auto bridge-group 1 ! interface FastEthernet0/1 no ip address shutdown duplex auto speed auto bridge-group 1 ! interface BVI1 ip address 192.168.1.1 255.255.255.248 no ip redirects no ip unreachables no ip proxy-arp ! ip forward-protocol nd ip route 0.0.0.0 0.0.0.0 192.168.1.254 ! ! control-plane ! bridge 1 protocol ieee bridge 1 route ip !