Olipro
  • Member for 8 years, 8 months
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How to check for a valid public IP address?
14 votes

Team Cymru provides a bogon reference for both IPv4 and IPv6 that you can use to filter out unassigned/reserved/private IP addresses - it's offered both as a simple list for well-known prefixes and ...

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Spanning Tree between only 2 HP switches connected via Etherchannel?
13 votes

Yes, configure it, just because your port channel is good doesn't mean your entire topology necessarily is - just connect another cable between the two switches on an active VLAN and watch the badness ...

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How to find the port a device is connected to, based on IP, on a Cisco Catalyst switch
13 votes

Firstly, you need to get the MAC address, so get into a machine on the same VLAN and look at its neighbour table - Windows is netsh int ipv4 show neigh, Linux: ip nei Cisco: show ip arp x.x.x.x. Once ...

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What is backpressure in the context of routers?
Accepted answer
11 votes

Backpressure refers to what is essentially concentration of traffic. E.g. I can have 10 x 1Gbit links internally that are all feeding into a 1Gbit link that provides me with Internet transit. at ...

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Distributed L3 Switching
11 votes

A lot of the content in this question is very Cisco-ish, let's dial that back and dispel some mythical assumptions. 1. I need to do Layer 2 at the core Not unless that's all your hardware is capable ...

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I'm setting up a Cisco CCNA lab, what equipment would you recommend?
10 votes

One thing to bear in mind with the CCNA is that the vast majority of the things you need to play with are trivially done in Cisco Packet Tracer and GNS3 (especially since you can now get a switchport ...

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Switch-Assisted Load Balancing w/ Fault Tolerance
Accepted answer
8 votes

At layer 2, all load balancing is, at best, done by an XOR or hash of the source and destination MAC, and if you're lucky, it may even read into layer 3 and hash that data too. At layer 3, however, ...

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How to mitigate UDP Flood?
8 votes

UDP attacks generally fit two profiles: Small packets aimed at hammering the application of the server. Large packets aimed at exhausting available bandwidth. There is of course also the possibility ...

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Which address should I use to receive a UDP wireless multicast with iperf?
Accepted answer
8 votes

I had this problem using multicast with iperf myself - in my case it was due to the fact that iperf does not let you bind to a multicast source on a specific interface and instead just hardcodes ...

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Is GRE necessary for an IP-only tunnel?
8 votes

Running a tunnel over GRE has the added benefit of being pretty much protocol-agnostic, so you can of course use it for IPv6 later on. With that said however, there's equally nothing stopping you ...

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Do unused Cisco IOS features take up RAM/CPU resources?
7 votes

Larger images will consume more RAM - it does not impact the CPU once loaded although it will also incur a longer boot time since it of course has to be decompressed into memory and that takes time. ...

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How to filter non-bogon prefixes received via BGP from an Internet Exchange(IXP)?
7 votes

Depending on how you're using the peering exchange, you've got a few different options: Firstly I'll cover RPKI and say that whilst it's something you should definitely go ahead and deploy, both for ...

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Migration from IPv4 to IPv6 strategies
7 votes

IPv6 migration at a high level? Enable IPv6 throughout the network, until IPv6 capabilities and connectivity are on par with IPv4. Wait for the day to come when IPv4 is no longer relevant. Now for ...

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Mitigating bad/malicious IPv6 RA announcements
7 votes

Cisco offers RA-guard as a means to protect against unprivileged ports sending out rogue RAs. However, enabling this alone isn't guaranteed to protect you as there are several attack tools in ...

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When is /31 recommended over /30 in P2P links?
Accepted answer
6 votes

Generally it comes down to interoperability - if you can guarantee that using a /31 is fine for both hosts on the link, and you are 100% sure that if one of the hosts fail, you will not be replacing ...

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upgrade RAM on a Cisco ASA 5520
Accepted answer
6 votes

Assuming it's a real 5520 and not a fake that's actually a converted 5510 (yep, a bunch of those were floating around - you'll know it by the fact it's only got a single RAM slot) you'll want PC3200 ...

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How much would a wiring fault cause bandwidth over cat 6 to drop by?
Accepted answer
4 votes

The way to determine this is to examine interface statistics for FEC failures. Generally speaking, 1000GBASE-T is relatively tolerant of wiring that's a little noisy, but you will see CRC32 errors - ...

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ipv6 addressing /127 vs eui-64
4 votes

Using a /127 isn't terrible, but letting it go into your backbone as a /127 is. The reason for this is that, essentially, most modern router TCAMs can typically only handle up to 64 bits of address ...

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Is ICMP spoofing practical?
4 votes

In any modern stateful NAT implementation, connection tracking is generally a fundamental part of facilitating it. There's not really any limitations on what IP protocols can be handled by NAT - Linux ...

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Cisco - display ALL routes using a single command
3 votes

show ip route for the IPv4 FIB. show ipv6 route for the IPv6 FIB. VRF routes: show <ip/ipv6> route vrf <*/vrfName> of course, * shows all VRFs.

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Subnetting a IPv4 /24 into 7 equally large subnets
3 votes

This is basic subnetting/binary logic. There's 2 /25s in a /24, 2 /26s in a /25 (ergo 4 /26s in a /24) and so forth. The closest match to the requirements is to use /27 which will leave you with one ...

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Inbound BGP load-balancing from same ISP router
3 votes

The optimum solution here is BGP ECMP via maximum-paths 2 - however, I will say that "accepting routes > /24" requiring a community tag sounds like epic stupidity - assuming you're a customer of ...

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/31 Point-to-point bitmasks
3 votes

Given the prudence and importance of address conservation, the general approach to using a /31 should be "if it works, use it". Of course, you could take this a step further and start using private ...

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How to choose a BGP router ID when using IPv6 only?
2 votes

My suggestion would be to adapt your AS number by treating it as a 32 bit AS (if it isn't already) - zero the upper 8 bits and OR with 0xE0000000 (makes it look like multicast space). For simplicity ...

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Only One Path in the Looking Glass
2 votes

Typically, BGP peers can only send a single path to eachother, with any updates for that path replacing the existing one. However, there is an extension to BGP, typically known as additional-paths ...

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Strange IPv6 packet seen when enabling interface on Juniper MX
1 votes

This is not so much related to MLD so much as it is to listening on the built-in IPv6 multicast groups. ff02::1 is the all-nodes multicast - I'm actually surprised you don't see that too (are you ...

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/23 PI space - breakup
1 votes

Pragmatically speaking, nothing needs to be done at the RIR, you just announce the /24 from whereeveand you're done. Good practice, on the other hand dictates that you should create a new route ...

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loopback ip issue
0 votes

When you assign the IP to the ethernet interface as a /30, The router sends out an ARP query for the MAC address of the neighbouring IP since it's on-link and thus requires a known MAC address in ...

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How can I diagnose a bridging (ethernet) loop?
0 votes

Determining a loop really depends on the brand of switch that you have. For example, on an Extreme switch, I can run elrp-client on a VLAN and the switch will basically send out a broadcast frame on ...

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Questions about datacenter switching and TRILL
-2 votes

TRILL strikes me as something that is barking up the wrong tree; it's costly in terms of both system resources and the complexity of hardware required to support it since it requires a total do-over ...

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