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Questions tagged [is-is]

For questions about the Intermediate System to Intermediate System (IS-IS) routing protocol.

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IS-IS as a PE-CE routing protocol

In case of IS-IS as a PE-CE routing protocol for MPLS VPNs , when route is redistributed from BGP to IS-IS , does 'Down Bit' is also set to avoid routing loops?. Background Information We know that ...
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30 views

IS-IS Interface Metric/Cost Calculation Issue in Juniper MX

I am facing a very strange issue with regard to IS-IS Interface Metric / Cost calculation in Juniper MX. We have configured a reference bandwidth of 1000G on all routers.This by definition means an ae ...
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1answer
425 views

How to implement Layer 3 (OSPF, IS-IS) link redundancy?

I think this kind of topic may be a course basic, but I'm still have a lot of technical doubts on how to implement redundant links on Layer 3, for example: -In order to use dual homing for a remote ...
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1answer
158 views

What is the difference between ISIS neighborship and adjacency?

Is there a difference between neighborship and adjacency in case os IS-IS? Many times I come across both the words in the context of IS-IS. Do they have different meanings based on the IS-IS states?
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1answer
512 views

How many maximum number of ISIS routers can be in an area or level?

As far as OSPF, I know that Cisco recommends that you should not have an OSPF area with more than 90-100 routers. Is there such restriction or recommendation for ISIS areas or levels?
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1answer
359 views

Does LDP not generate a label for default route for ISIS Level 2?

LDP generates local bindings for all the routes in the routing table. I configured an ISIS topology such that: R1 ----- R2 ----- R3 ----- R4 ----- R5 L1 L1/2 L2 L1/2 L1 ...
5
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2answers
177 views

In Multi Area IS-IS how does an L1 router choose the L1/L2 to use for interarea routing?

This is related to a similar question IS-IS multi area But instead of the how is the destination router chosen, I want to know how L1 routers choose the first L1/L2 router. Using the below topology: ...
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1answer
42 views

What happened if I set up multiple links between an IS to other IS?

I don't have machines to test this yet. But I would like to ask what would happened if I set up multiple links between an IS to other IS? Something like this one: -- --Link 1-- -- --- |R1| --...
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256 views

Problem configuring L3VPN with MPLS, RSVP-TE, VLAN

We are having problems to configure a L3VPN in VIRL with an MPLS CORE NETWORK that uses RSVP-TE as label exchange protocol and IS-IS as IGP protocol. The idea is to distinguish different type of ...
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4answers
150 views

IS-IS IPv6 over IPv4

In IS-IS the router knows the interfaces addresses of the other routers. So would it be possible to connect two IPv6 areas over an IPv4 area? A router in area A knows that the destination ipv6 ...
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1answer
227 views

Regarding clns mtu

I understand the below points,please confirm if my understanding is correct. MTU > MSS E.g if my MSS is 1460 bytes, then MTU should be at least 1500 bytes(20 bytes for IP header and 20 bytes for TCP ...
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2answers
1k views

Understanding route metric 0

I have the below output from an IOS-XR box: RP/0/RSP0/CPU0:RTR1#show route 10.10.10.10 Wed Mar 27 13:34:52.553 IST Routing entry for 10.10.10.10/32 Known via "isis IGP", distance 115, metric 261, ...
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0answers
66 views

Policy routing with IS-IS

three routers are connected where Router A connected to router B A (gig0/0/0 ip address 10.10.1.1)====> B(gig0/0/0 ip address 10.10.1.2 A(gig0/0/0=> ip address 10.11.1.1===>B(gig0/0/...
2
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1answer
364 views

ISIS Max metric

I need to confirm the below as i don't have access to a lab. I have 4 XR boxes connected linearly as shown.Router A is advertsing PC subnet in isis. My understanding: So when the subnet of PC A ...
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1answer
2k views

How to enable isis in packettracer

I am using cisco packet tracer 7.0. I am supposed to set isis as the routing protocol. But when try to do this in config mode, the router does not identify the command "router isis". When I enter ...
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2answers
241 views

Does the Shortest Path First algorithm (SPF) Algorithm for OSPF and IS-IS generate all shortest paths between nodes, or just one?

To be more specific. If there are two equal cost paths between two nodes, does the SPF Algorithm give the next hop value for both paths?
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2answers
264 views

IS-IS multi-area

It is well known that an IS-IS L1 router chooses the nearest L1/L2 router to route inter-area traffic, if there is no route leaking as defined in RFC 2966. However, providing that there is no route ...
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2answers
216 views

IS-IS Hello packets and IPv4/IPv6 addresses

IS-IS Hello packets contain IPv4(and IPv6 address). For example see the "IPv4 Interface" field in this IS-IS Hello packet: $ tcpdump -c1 -vvvr isis.pcap reading from file isis.pcap, link-type EN10MB (...
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1answer
633 views

MPLS load balancing on Huawei S5700

On a L3 switch there are two equal cost ISIS routes. Destination/Mask Proto Pre Cost Flags NextHop Interface 10.150.4.12/32 ISIS-L2 15 10 D 10.200.15.42 Vlanif27 ...
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1answer
586 views

Juniper IS-IS levels hierarchy configuration

Can someone please tell me what is the interface ge-2/1/0.0 IS-IS level after we have applied this config? Does Juniper takes both commands? level 2 disable at the interface level level 1 disable ...
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2answers
5k views

How does IS-IS carry IP routes?

IS-IS runs natively on layer 2 of the OSI reference model. How will the routing be done in that? My doubt is that layer 3 has the ability to do the routing. But, ISIS does not run in layer 3 rather ...
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1answer
2k views

Cisco & Juniper: IPv6 link-local addresses used between ISIS neighbours

I am configuring IPv6 between a Juniper MX80 and Cisco 7206VXR which already happily run IPv4 over ISIS and iBGP. ISIS is carrying IPv6 routes between the two devices but I have what I believe is a ...