On 9/30/10 12:57 AM, Mark Smith wrote: On Thu, 30 Sep 2010 14:13:11 +1000 Julien Goodwin [1]<nanog@studio442.com.au> wrote: On 30/09/10 13:42, Mark Smith wrote: One of the large delays you see in OSPF is election of the designated router on multi-access links such as ethernets. As ethernet is being very commonly used for point-to-point non-edge links, you can eliminate that delay and also the corresponding network LSA by making OSPF treat the link as a point-to-point link e.g. int ethernet0 ip ospf network point-to-point If your implementation doesn't support point-to-point mode for an interface, point-to-multipoint mode on an ethernet would achieve something somewhat equivalent. Do any implementations go point-to-point automatically if an ethernet has a /30 or /31 mask? Don't know. Nope. Not Cisco anyway. NDC-R1-CustA(config)#int f0/0 NDC-R1-CustA(config-if)#ip addr 10.111.1.1 255.255.255.254 % Warning: use /31 mask on non point-to-point interface cautiously NDC-R1-CustA(config-if)# *Sep 30 15:18:22.710: %OSPF-5-ADJCHG: Process 1, Nbr 10.133.1.2 on FastEthernet0/0 from FULL to DOWN, Neighbor Down: Interface down or detached NDC-R1-CustA(config-if)# NDC-R1-CustA(config-if)#do sh ip o i f0/0 | i Type|Address Internet Address 10.111.1.1/31, Area 0 Process ID 1, Router ID 192.168.1.1, Network Type BROADCAST, Cost: 1 NDC-R1-CustA(config-if)# HTH, Scott On 9/30/10 12:57 AM, Mark Smith wrote: On Thu, 30 Sep 2010 14:13:11 +1000 Julien Goodwin [2]<nanog@studio442.com.au> wrote: On 30/09/10 13:42, Mark Smith wrote: One of the large delays you see in OSPF is election of the designated router on multi-access links such as ethernets. As ethernet is being very commonly used for point-to-point non-edge links, you can eliminate that delay and also the corresponding network LSA by making OSPF treat the link as a point-to-point link e.g. int ethernet0 ip ospf network point-to-point If your implementation doesn't support point-to-point mode for an interface, point-to-multipoint mode on an ethernet would achieve something somewhat equivalent. Do any implementations go point-to-point automatically if an ethernet has a /30 or /31 mask? Don't know. If you want to see what interface model OSPF is using, on a Cisco you use show ip ospf interface <blah> The interface type for loopback interfaces can be a bit surprising and the consequences a bit unexpected if you're intentionally or otherwise not using a /32 prefix length on one. Regards, Mark. References 1. mailto:nanog@studio442.com.au 2. mailto:nanog@studio442.com.au