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 Post subject: OSPF areas - how to achieve optimal routing - Cisco way
PostPosted: Tue Nov 18, 2014 11:30 am 
OSPF areas - how to achieve optimal routing - Cisco way

Image

In previous article "OSPF areas: Analysing an apprently redundant design - Cisco way" http://forum.ivorde.ro/ospf-areas-analysing-an-apprently-redundant-design-cisco-way-t19241.html I discussed about a an OSPF design that has some caveats.

I will continue here with an aspect that can be seen in many networks: What path will traffic from R5 to R4 take ? (virtual link between R1 and R3 is not configured).


R5#traceroute 4.4.4.4 source 5.5.5.5 ...

Read more : OSPF areas - how to achieve optimal routing - Cisco way | Views : 1644 | Replies : 1

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 Post subject: OSPF areas: Analysing an apprently redundant design - Cisco way
PostPosted: Tue Nov 18, 2014 11:14 am 
OSPF areas: Analysing an apprently redundant design - Cisco way
Attachment:
ospf-area-design-cisco.png

Ok. So we know a little bit about OSPF from previous articles. Here is a recap:

- All internal destinations within an area are advertised througy Type 1 LSA (Router LSA) in OSPF.
- These internal destinations reach the ABR (Area Border Router) and they are injected as type 3 LSA (Summary LSA) into area 0 (backbone area) from any ...

Read more : OSPF areas: Analysing an apprently redundant design - Cisco way | Views : 2133 | Replies : 0

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 Post subject: OSPF: Dangers of non-standard area design - Juniper way
PostPosted: Thu Nov 13, 2014 12:29 pm 
OSPF: Dangers of having non-redundant backbone ABRs isolated areas

Attachment:
ospf-non-standard-area-design.png


This is Part 2 of an OSPF story. Part 1 can be found here: http://forum.ivorde.ro/ospf-multi-area-scenario-with-isolated-areas-cisco-juniper-part-1-t19221.html


In the top diagram I have a non-standard OSPF network (only OSPF AS internal routes) that works well and optimized if all links and nodes are up.

I will show throughout this part some failing scenarios and how parts of the network can remain separated from ...

Read more : OSPF: Dangers of non-standard area design - Juniper way | Views : 1649 | Replies : 0

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 Post subject: OSPF Multi area scenario with isolated areas cisco & Juniper - part 1.
PostPosted: Thu Nov 13, 2014 9:51 am 
OSPF Multi area scenario with isolated areas cisco & Juniper - part 1.


Before I start this is a list of very good references on this subject, imho:
http://blog.ine.com/wp-content/uploads/2011/01/Loop-Prevention-in-OSPF.pdf
http://blog.ipexpert.com/what-makes-a-router-an-ospf-abr-cisco-and-juniper-comparison/
https://tools.ietf.org/html/rfc3509#ref-Ref1
http://www.research.att.com/techdocs/TD_100766.pptx


Lately I've went through a hand full of articles describing OSPF loop avoidance architecture and about it being a link state protocol. Hoewever it's hard to find a good read that answers questions like "what if ?".

OSPF is both a link state ...

Read more : OSPF Multi area scenario with isolated areas cisco & Juniper - part 1. | Views : 2121 | Replies : 0

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 Post subject: Junos: BGP label allocation failure: Need a nexthop address on LAN
PostPosted: Thu Nov 06, 2014 11:52 am 
Code:
[edit]
admin@R3# run show route advertising-protocol bgp 10.255.0.4 extensive

VRF-1-osiris.inet.0: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden)
* 10.43.3.0/24 (1 entry, 1 announced)
BGP group internal type Internal
     Route Distinguisher: 10.255.0.3:1
     BGP label allocation failure: Need a nexthop address on LAN
     Nexthop: Not advertised
     Flags: Nexthop Change
     Localpref: 100
     AS path: [1234567890] I
     Communities: target:1:1


This error is caused by the fact that local VPN routes sitting on a broadcast (Ethernet) ...

Read more : Junos: BGP label allocation failure: Need a nexthop address on LAN | Views : 2149 | Replies : 1

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 Post subject: Junos router advertisements - Unix IPv6 stateless autoconfiguration via SLAAC
PostPosted: Mon Jun 23, 2014 5:23 am 
One of the differences brought by IPv6 is the Extended Unique Identifier (EUI) (RFC2373). EUI-64 allows a host to assign iteslf a unique 64-Bit IP Version 6 interface identifier - based on it's MAC address. This algorithm is used to generate the link local IPv6 address and can also be used with a stateless mechanism.

With SLAAC (Stateless Address Auto Configuration), a host sitting in a layer2 domain assigns that specific interface a global IPv6 ...

Read more : Junos router advertisements - Unix IPv6 stateless autoconfiguration via SLAAC | Views : 4337 | Replies : 0

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 Post subject: Example of BGP update message sent from Junos for a VPLS circuit
PostPosted: Fri Jul 19, 2013 9:24 am 
Example of BGP update message sent from Junos for a VPLS circuit

Note the use of the BGP extended target communities

Border Gateway Protocol - UPDATE Message
Marker: ffffffffffffffffffffffffffffffff
Length: 88
Type: UPDATE Message (2)
Unfeasible routes length: 0 bytes
Total path attribute length: 65 bytes
Path attributes
ORIGIN: IGP (4 bytes)
Flags: 0x40 (Well-known, Transitive, Complete)
Type code: ORIGIN (1)
Length: 1 byte
Origin: IGP (0)
AS_PATH: empty (3 bytes)
Flags: 0x40 (Well-known, Transitive, ...

Read more : Example of BGP update message sent from Junos for a VPLS circuit | Views : 1369 | Replies : 0

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 Post subject: Example of BGP update message sent from Junos device when export policy is modified
PostPosted: Fri Jul 19, 2013 9:09 am 
Example of BGP update message sent from Junos device when export policy is modified

On an existing established neighbour, I have changed the export policy to attach a community for two routes. One bgp update message per route. Below is an example.
Border Gateway Protocol - UPDATE Message
Marker: ffffffffffffffffffffffffffffffff
Length: 62
Type: UPDATE Message (2)
Unfeasible routes length: 0 bytes
Total path attribute length: 35 bytes
Path attributes
ORIGIN: IGP (4 bytes)
Flags: 0x40 ...

Read more : Example of BGP update message sent from Junos device when export policy is modified | Views : 1255 | Replies : 0

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 Post subject: Junos VPLS Virtual circuit stuck in "VC-Dn" state
PostPosted: Tue Jul 09, 2013 9:48 am 
# run show vpls connections
Layer-2 VPN connections:

Legend for connection status (St)
EI -- encapsulation invalid NC -- interface encapsulation not CCC/TCC/VPLS
EM -- encapsulation mismatch WE -- interface and instance encaps not same
VC-Dn -- Virtual circuit down NP -- interface hardware not present
CM -- control-word mismatch -> -- only outbound connection is up
CN -- circuit not provisioned <- -- only inbound connection is up
OR -- out of range Up ...

Read more : Junos VPLS Virtual circuit stuck in "VC-Dn" state | Views : 3313 | Replies : 0

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 Post subject: Junos VPLS Label Block Operations - Example with BGP signaling
PostPosted: Thu Jul 04, 2013 7:44 am 
Juniper book makes a good explanation on the Label Block operation in VPLS vpn.
Understanding VPLS Label Block Operationshttp://kb.juniper.net/library/CUSTOMERSERVICE/technotes/Understanding_VPLS_Label_Blocks_Operation.pdf
http://www.juniper.net/techpubs/en_US/junos/topics/concept/vpls-label-blocks-overview.html

Let's see this in a real example with BGP used for signaling. Below is a BGP update message containing a VPLS NLRI from a site ID 10 that is received by a site ID 11:

Border Gateway Protocol - UPDATE Message
Marker: ffffffffffffffffffffffffffffffff
Length: 88
Type: UPDATE Message (2)
Unfeasible routes length: 0 bytes
Total ...

Read more : Junos VPLS Label Block Operations - Example with BGP signaling | Views : 2740 | Replies : 0

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