Routing

in ospf

Hi Rob,

 

This field is used to identify the external route as Type 1 or Type 2.

The least significant bit is set to value of 1 indicating Type-2 External LSA, while it sets to value of 0 indicating Type-1 External LSA.

 

In your case it is Type-5 External LSA with Type-2 metric.

 

Type-2 External LSA = Route Cost is same as metric advertised in LSA.
Type-1 External LSA = Route Cost is sum of metric advertised in LSA and metric of ASBR.

 

More Ref:

http://tools.ietf.org/html/draft-ietf-l3vpn-ospf-2547-04#section-4.2.6

         * Options: 1 byte. Currently this is only used if the route
           type is 5 or 7. Setting the least significant bit in the
           field indicates that the route carries a type 2 metric.

 

 

Regards

Surya

Type-2 External LSA = Route Cost is same as metric advertised in LSA. Type-1 External LSA = Route Cost is sum of metric advertised in LSA and metric of ASBR. by default,which type it will use?

Hi Rob,

 

       Please refer: 

 

http://tools.ietf.org/html/draft-ietf-l3vpn-ospf-2547-04#section-4.2.8.1

 

 

By default, a type 2 metric value is included in the LSA, unless the

options field of the OSPF Route Type Extended Communities attribute

 of the VPN-IPv4 route specifies that the metric should be type 1.

 

 

Regards

Surya

if I want to change it to type 1,how  and where?

......

Hi Rob,

 

If the route from CE1 is Type-1 External route, then it would be "0" else if it is Type-2, then it would be "1"

 

Type 2  Example:

 

suryak@PE1> show ospf database external instance VPNA extensive lsa-id 211.1.1.1
    OSPF AS SCOPE link state database
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
Extern   211.1.1.1        6.6.6.6          0x80000003   763  0x22 0x655c  36
  mask 255.255.255.255
  Topology default (ID 0)
    Type: 2, Metric: 0, Fwd addr: 0.0.0.0, Tag: 0.0.0.0
  Aging timer 00:47:16
  Installed 00:12:42 ago, expires in 00:47:17
  Last changed 00:12:42 ago, Change count: 3

suryak@PE1> show route advertising-protocol bgp 3.3.3.3 211.1.1.1 detail

VPNA.inet.0: 6 destinations, 6 routes (6 active, 0 holddown, 0 hidden)
* 211.1.1.1/32 (1 entry, 1 announced)
 BGP group int type Internal
     Route Distinguisher: 100:1
     VPN Label: 300032
     Nexthop: Self
     Flags: Nexthop Change
     MED: 0
     Localpref: 100
     AS path: [100] I
     Communities: target:100:100 rte-type:0.0.0.0:5:1


suryak@PE2> show route table bgp.l3vpn.0 rd-prefix 100:1:211.1.1.1/32 detail       

bgp.l3vpn.0: 4 destinations, 4 routes (4 active, 0 holddown, 0 hidden)
100:1:211.1.1.1/32 (1 entry, 0 announced)
        *BGP    Preference: 170/-101
                Route Distinguisher: 100:1
                Next hop type: Indirect
                Address: 0x944d2c4
                Next-hop reference count: 12
                Source: 1.1.1.1
                Next hop type: Router, Next hop index: 578
                Next hop: 20.0.2.1 via ge-3/1/2.0 weight 0x1, selected
                Label-switched-path lsp1
                Label operation: Push 300032, Push 301264(top)
                Label TTL action: prop-ttl, prop-ttl(top)
                Session Id: 0x52
                Protocol next hop: 1.1.1.1
                Push 300032
                Indirect next hop: 959c000 2097150 INH Session ID: 0x55
                State: <Active Int Ext>
                Local AS:   100 Peer AS:   100
                Age: 14:15      Metric: 0       Metric2: 65535
                Validation State: unverified
                Task: BGP_100.1.1.1.1+179
                AS path: I
                Communities: target:100:100 rte-type:0.0.0.0:5:1
                Import Accepted
                VPN Label: 300032
                Localpref: 100
                Router ID: 1.1.1.1
                Secondary Tables: VPNA.inet.0



suryak@CE2> show ospf database external lsa-id 211.1.1.1 detail logical-system sys1       
    OSPF AS SCOPE link state database
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
Extern   211.1.1.1        172.169.1.1      0x80000003   895  0xa2 0x715a  36
  mask 255.255.255.255
  Topology default (ID 0)
    Type: 2, Metric: 0, Fwd addr: 0.0.0.0, Tag: 208.0.0.100



suryak@CE2> show route 211.1.1.1 logical-system sys1           

inet.0: 7 destinations, 7 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

211.1.1.1/32       *[OSPF/150] 00:15:17, metric 0, tag 3489661028
                    > to 172.169.1.1 via ge-3/1/3.0

 

Type 1 Example:

suryak@PE1> show ospf database external instance VPNA extensive lsa-id 211.1.1.1    
    OSPF AS SCOPE link state database
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
Extern   211.1.1.1        6.6.6.6          0x80000004    12  0x22 0xdf61  36
  mask 255.255.255.255
  Topology default (ID 0)
    Type: 1, Metric: 0, Fwd addr: 0.0.0.0, Tag: 0.0.0.0
  Aging timer 00:59:47
  Installed 00:00:11 ago, expires in 00:59:48
  Last changed 00:00:11 ago, Change count: 4

suryak@PE1> show route advertising-protocol bgp 3.3.3.3 211.1.1.1 detail            

VPNA.inet.0: 6 destinations, 6 routes (6 active, 0 holddown, 0 hidden)
* 211.1.1.1/32 (1 entry, 1 announced)
 BGP group int type Internal
     Route Distinguisher: 100:1
     VPN Label: 300032
     Nexthop: Self
     Flags: Nexthop Change
     MED: 1
     Localpref: 100
     AS path: [100] I
     Communities: target:100:100 rte-type:0.0.0.0:5:0


suryak@PE2> show route table bgp.l3vpn.0 rd-prefix 100:1:211.1.1.1/32 detail    

bgp.l3vpn.0: 4 destinations, 4 routes (4 active, 0 holddown, 0 hidden)
100:1:211.1.1.1/32 (1 entry, 0 announced)
        *BGP    Preference: 170/-101
                Route Distinguisher: 100:1
                Next hop type: Indirect
                Address: 0x944d2c4
                Next-hop reference count: 12
                Source: 1.1.1.1
                Next hop type: Router, Next hop index: 578
                Next hop: 20.0.2.1 via ge-3/1/2.0 weight 0x1, selected
                Label-switched-path lsp1
                Label operation: Push 300032, Push 301264(top)
                Label TTL action: prop-ttl, prop-ttl(top)
                Session Id: 0x52
                Protocol next hop: 1.1.1.1
                Push 300032
                Indirect next hop: 959c000 2097150 INH Session ID: 0x55
                State: <Active Int Ext>
                Local AS:   100 Peer AS:   100
                Age: 26         Metric: 1       Metric2: 65535
                Validation State: unverified
                Task: BGP_100.1.1.1.1+179
                AS path: I
                Communities: target:100:100 rte-type:0.0.0.0:5:0
                Import Accepted
                VPN Label: 300032
                Localpref: 100
                Router ID: 1.1.1.1
                Secondary Tables: VPNA.inet.0


suryak@CE2> show ospf database external lsa-id 211.1.1.1 detail logical-system sys1    
    OSPF AS SCOPE link state database
 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len
Extern   211.1.1.1        172.169.1.1      0x80000004    39  0xa2 0xf554  36
  mask 255.255.255.255
  Topology default (ID 0)
    Type: 1, Metric: 1, Fwd addr: 0.0.0.0, Tag: 208.0.0.100

suryak@CE2> show route 211.1.1.1 logical-system sys1                                   

inet.0: 7 destinations, 7 routes (7 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

211.1.1.1/32       *[OSPF/150] 00:00:40, metric 2, tag 3489661028
                    > to 172.169.1.1 via ge-3/1/3.0

Hi,Surya by default it is type 2 how to change it to type 1? it seems "Metric2" is useless in this prefix,I only see "Metric"

Hi Rob,

 

IMHO I don't think you have a option to change  rather the type of CE route decides 1 or 0.

 

As per below, the MED (Metric) value is used as route metric.

 

http://tools.ietf.org/html/draft-ietf-l3vpn-ospf-2547-04#section-4.2.6

 

   By default, the value of the metric its value is taken from the MED
   attribute of the VPN-IPv4 route.