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.

Filter by
Sorted by
Tagged with
0
votes
0answers
8 views

Is it possible for a routing loop to form using ADOV (Ad Hoc on Demand Distance Vector Routing) if there is a corruption in the sequence number?

I know that the sequence number prevents routing loops and I roughly understand how it functions. However, say there is a corruption in one of the nodes in its sequence number for a particular route. ...
1
vote
2answers
41 views

How would a bridge loop occur?

As I understand it, STP is used to prevent bridge (/switch) loops, which will typically occur in the case of redundant links on a switch. But how can a loop occur and cause a broadcast storm? If a ...
0
votes
0answers
19 views

Cisco SPA3xx/5xx microphone input loopback

Not entirely sure where to place this question. But since this StackExchange branch is pretty much the only with questions regarding Cisco IP phones, I might give it a try here. Feel free to suggest ...
0
votes
1answer
65 views

How to create a routing loop? [closed]

Let's say I have two or three routers and I want the packets sent between them NOT to reach their destination but to "loop" between the routers until TTL runs out." I need to do this in a network ...
1
vote
1answer
171 views

Cisco ASA looping broadcast packet

I have small office where running cisco ASA ASA5506 and version 9.4(1) and it's also configured for IPsec VPN tunnel, My LAN subnet is 10.1.1.0/24 So i have found very interesting things in LAN ...
1
vote
0answers
62 views

IS-IS as a PE-CE routing protocol [closed]

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 ...
4
votes
2answers
387 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 ...
5
votes
1answer
497 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. ...
1
vote
2answers
192 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?
1
vote
2answers
378 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 ...
3
votes
1answer
1k 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
votes
1answer
112 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 ...
1
vote
2answers
973 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 ...
1
vote
1answer
559 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 ...
0
votes
1answer
525 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 ...
1
vote
2answers
4k 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 ...
1
vote
1answer
208 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 ...
1
vote
3answers
485 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 ...
1
vote
2answers
6k 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 ...
3
votes
2answers
6k 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 ...
3
votes
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 ...
1
vote
2answers
503 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<-&...
2
votes
1answer
784 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 ...
2
votes
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 ...
8
votes
2answers
1k 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-...
5
votes
1answer
834 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 ...
5
votes
1answer
526 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. ...
11
votes
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 ...