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1500 questions
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3 answers

What factors drive a Cisco IOS upgrade?

In order of preference/priority, what factors do you consider in driving an upgrade (or downgrade) with Cisco IOS? If no compelling factors exist, how long would you allow a particular version of IOS to stay running? I've seen some switches with…
generalnetworkerror
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What is the difference between all the switching modes on 6500/7600?

On one of my routers, I see the following switching modes: #show fabric switching-mode Global switching mode is Truncated dCEF mode is not enforced for system to operate Fabric module is not required for system to operate Modules are allowed to…
Aaron
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19
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4 answers

Jumbo Ethernet Frame Deployment

What are some general guidelines for the successful deployment of jumbo frames in a routed environment?
Dennis Olvany
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19
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2 answers

How does a WiFi range extender work?

I have a WiFi base station, and a WiFi range extender. Both of them have the same SSID. When a device connects to that SSID, what exactly happens? How does the device know that base station and range extender are part of the same network and no…
Johannes Ernst
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19
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2 answers

Traceroute - every packet has TTL == 1

I'm working on Wireshark lab-IP in Computer networking - A top down approach and I don't understand why every packet that normally expired has a TTL of 1. Here is my Wireshark capture…
ksp0422
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18
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6 answers

How are IP addresses mapped to MAC addresses?

I've been reading about the differences between MAC and IP addresses, and why we need both of them. To summarize, MAC addresses are physical unchangeable unique IDs for every single device while IP addresses are assigned, changeable and virtual. To…
CodyBugstein
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18
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Why do some common traceroute implementations default to using UDP probes?

I was recently troubleshooting a network connectivity meta-problem, in that I knew a given destination was reachable, but I was not able to demonstrate that with traceroute because the path went cold after a certain number of hops. Given that the…
neirbowj
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18
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3 answers

How do you know if a Cisco switch is handling traffic well?

I have just read Jeremy's question about 2960-S and iSCSI traffic handling, which drove me to ask this question: We all have lots of switches deployed in distinct infrastructures, how can you know that the traffic is treated well? I usually check…
laf
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18
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3 answers

Why does an Ethernet cable have four pairs?

I'm curious about why 10Base-T and then 100Base-T Ethernet networks used cables which had four pairs if they only needed two? Were there some cables that only had two pairs? If we wanted to increase the speed of Ethernet further in the future, could…
UnderAnOpenSky
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4 answers

MAC address recycling?

Something I've always wondered about is MAC address exhaustion. Do hardware vendors keep track of MAC address allocation to their platforms, and then subsequently "reclaim" MAC addresses when a product goes EOL, and then re-use them on a new…
John Jensen
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4 answers

IPv6: Why not use /126 on P2P links for IPv6?

In IPv4 we use /30 to conserve addresses. So why do some people recommend using /64 on P2P links instead of /126? I get using a /64 on regular subnets but isn't using a /64 when there will only ever be two addresses in use on P2P links tremendous…
bahamat
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4 answers

Are there any reasons to not use BFD?

In looking to implement Bidirectional Forwarding Detection (BFD) it seems to be very flexible in terms of timer tuning, light weight regarding any overhead and it's flexibility in terms of overall application appears very impressive. So if for…
MattE
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18
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1 answer

MPLS auto-bandwidth balancing

I operate an MPLS/IP network that utilizes auto-bandwidth to measure bandwidth utilization and signal RSVP accordingly. How can I maintain balance across my LSP paths such that one large [P router]-to-[P router] path/flow doesn't saturate any one…
jof
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18
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1 answer

What does TCP DUP ACK mean?

In Wireshark, I see TCP duplicate ACK packets sent from the receiver to the sender. What does it mean? Does it imply packet loss? Thank you
John T
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18
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3 answers

Adding a simple VLAN on a Juniper MX

after years away from JunOS, working with Foundry (now Brocade) routers, I find myself with a new Juniper MX10. All I want to do is create a simple VLAN such that two ports share one routing interface, which has one IP address. On a Brocade, this…
Matt
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