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Questions tagged [loop]

For questions about or involving network loops. For instance, you are troubleshooting a switching loop, where more than one device create a layer 2 loop or you are trying to fix a routing loop in your network.

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18 views

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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2answers
328 views

Why does EIGRP aim to be loop free?

As far as I understand: EIGRP is a routing protocol and handles IP packets. IP packets are outfitted with the TTL field and thus, do not loop indefinitely like layer 2 frames do. Why does EIGRP try ...
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1answer
286 views

How does STP convergence work?

Consider the IEEE 802.1D (first revision) Spanning Tree Protocol. I have read a lot of articles and forum entries about STP convergence. Often I do find contradictions about the convergence mechanics. ...
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2answers
86 views

Is a networking loop considered a DoS attack?

Is a networking loop considered a DoS attack? I watched this tutorial and at 1:20: The author says that a network loop, could be a DoS in a network?
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2answers
254 views

How to avoid a routing loop in a 'subnet of a subnet'?

This question is motivated by the example given near the end of Cisco's article on Subnet Zero and the All-Ones Subnet (from the subsection titled The All-Ones Subnet), but I include all necessary ...
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1answer
737 views

Connecting an SRX chassis cluster to redundant upstream WAN links

I've been tasked with migrating some Juniper SSG 140's in an active/passive cluster to an SRX 340 cluster. I'm very familiar with ScreenOS, but am still learning JunOS. Currently, we're connected to ...
2
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1answer
94 views

Routing the same prefix to different destinations on the same router

I have a Cisco Nexus 7000 and have configured static routes to reach my internal networks on the Nexus 7000. During a DDOS attack, the Nexus 7000 receives a more specific route via IBGP to re-route ...
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2answers
630 views

Prevent DHCP looping

Today my company had an annoying issue with DHCP looping. I spent more than 2 hours to figure out why several PCs get IPs from VOIP subnet. My manager spent about 30 minutes and figured out that ...
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1answer
412 views

RSTP 802.1w maximum network loop diameter

Can anybody direct me to a calculation of the maximum network diameter (number of devices) on an RSTP tree (RSTP, NOT STP)? As far as I can understand from the standard and the RFC, there is no such ...
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1answer
343 views

Is this topology loop free?

I have the following topology: Topology I intend to build this network with the PC acting as a DHCP server and multiple IP-enabled custom development boards connected to the switch and some ...
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2answers
3k views

vpc loop avoidance scenario

Consider the attached topology. There is a vPC domain, with vPC 20 for Sw2 and vPC 10 for Sw1. vPC peer link exists between NxOS1 and NxOS2. Suppose, Sw2 sends broadcast traffic.This broadcast ...
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1answer
189 views

Regarding Bridge Assurance feature

In one of the articles i read the following regarding Bridge assurance: "When enabled, BDPU’s are sent out all ports including the backup and alternate for each Hello Period. How this feature works ...
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3answers
367 views

Is STP used to prevent all traffic looping or just broadcast and multicast?

Let's say we have 3 switches in a logical triangle, each switch connected to the other two. This provides an opportunity for a loop when multicast or broadcast traffic is traveling here. STP is used ...
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2answers
4k views

Connect a LAN cable to LAN1 & LAN2

I connected a LAN cable from the LAN-1 port to the LAN-2 port owned by the same router. Then really weird things happened: For 10 - 15 seconds, nothing happened, none of the lights on the modem are ...
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2answers
2k views

Cisco: err-disabled due to loop - but there are NO redundant physical paths/ wires/ connections

for the third or fourth time in approx two years we have (painfully) noticed some really strange (at least to us) behaviour in our datacenters: Uplink-interfaces on access-switches which have only ...
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2answers
2k views

Duplicate packet / ping reply in network configuration

I'm having a issue with receiving duplicate packets in my network and I'm unsure what's causing it. A simplistic explanation of what's happening is this: Server1 sends a ping request to Server2 ...
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2answers
452 views

Avoiding switch loop?

Please advise on the following question: With 2 Cisco 2960G switches connected as in the diagram: STP is not used. How could the switches be configured in such a way that all the traffic HOST<-&...
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1answer
706 views

Distance Vector vs. Link State routing

Distance vector routing protocols have Split horizon & poison reverse for avoiding routing loops in the network. why the link state routing protocol not having that kind of measures and how the ...
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1answer
1k views

Does this make a VLAN loop?

I have a network that provides external IP addresses through VLANs. The same network also provides VLANs for internal use. Roughs map (not all switches): VLAN 20 (for ...
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2answers
987 views

RSTP Basics: Can this be done?

What I've got: Two 24 port switches in building A, with 2 fibre trunks from building A to building B - where there are two 48 port switches. The two 24 port switches support RSTP and STP. HP 1810-...
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1answer
739 views

What happens when you stop receiving BPDUs with no L1 loss?

We have a redundant path for some of our communications through a.) a Metro-E provider and b.) two routers forming an L2TPV3 tunnel. We have Cisco 2960 switches at both ends running RSTP to prevent ...
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1answer
503 views

Loop Prevention in AODV

we're supposed to do a presentation on AODV, and even having read all the official documentation and some additional sources, we're stumped by the question of how sequence numbers prevent loops. ...
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3answers
4k views

OSPF over vPC on Nexus7k

I'm trying to help a friend with some Nexus issues. The topology is like this: Cat 3750 stack -> vPC -> 2x N7k -> LACP -> Fortigate firewall cluster The 3750 stack is running OSPF to both the ...