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16
votes
8answers
17k views

When *not* to create a SVI for a L2 VLAN?

When creating VLANs for just L2 on a switch -- routing will be handled by a device within that VLAN such as a load-balancer -- it isn't necessary to create the vlan interface. As a matter of habit, I ...
4
votes
2answers
4k views

Cisco: No autostate on GigabitEthernet interfaces, any alternative? (not working)

I recently tried the command "no autostate" on a GigabitEthernet interface (on a newer router) and this didn't work anymore, does anyone know why this is occuring? This use to work on FastEthernet ...
16
votes
7answers
92k views

What are the differences between VRRP and HSRP?

Are there any significant differences between VRRP and HSRP?
20
votes
7answers
30k views

Difference between access list and prefix list?

Can someone explain with an example whats the difference between an access list and prefix list.
8
votes
3answers
6k views

BGP - Soft Reset Outbound & Verification

My understanding of the command: clear ip bgp * soft out is that the router on which the command is issued will re-advertise everything it knows about BGP to it's neighbors. As I see it, it's as if ...
10
votes
1answer
4k views

PPPoA ADSL Configuration with external modem on Cisco 891

Context We use Cisco 891 routers as CPE for several client sites. They are all running IOS 15. Cisco IOS Software, C890 Software (C890-UNIVERSALK9-M), Version 15.0(1)M8, RELEASE SOFTWARE (fc1) The ...
16
votes
12answers
34k views

What would cause high latency anytime there is traffic on WAN?

I have a network that has been experiencing slow internet speeds. After a great deal of troubleshooting, I have determined that any streaming content/downloads will cause the latency of WAN traffic to ...
12
votes
4answers
8k views

What is the use of wild card masks vs normal masks

I've always wondered what the use of wild card masks was. When I learned about them in college I wondered what the use was, we saw that you could separate subnets by for instance even and uneven IPs. ...
6
votes
1answer
559 views

After a memory upgrade of my Cisco WAAS, why is the connection limit still the same, how can I raise it?

We use Cisco WAAS appliances for WAN optimization. With increasing traffic, we noticed that the connection limit was frequently reached. In case of our WAVE-574-K9 with 3 GB RAM, there was a limit of ...
5
votes
3answers
564 views

address-family ipv6 on Cisco 3560G

Is anyone aware of an IOS version for the C3560G that supports configuring a neighbor to exchange IPv6 routes? Apparently 12.2(37)SE Advanced IP Services can't do it - as soon as you try to activate ...
5
votes
1answer
2k views

Running XML agent on IOS XR

I'm trying to configure the dedicated XML agent on IOS XR 4.2.3 (ASR9K) . The API guide says to do the xml agent aaa authorization exec default local which I did, and I can connect to the router ...
6
votes
1answer
2k views

Cisco 2148T FEX Port Capabilities Error

Does a Cisco 2148T FEX not support 100 Mb interface speed? When trying to manually configure a host port to run at 100/full on a 2148 FEX I receive an error that states: ERROR: Configuration does ...
8
votes
4answers
3k views

Expanding an HP IRF topology

I'm examining options for a future expansion of our infrastructure. We rent space at a colo so we don't have a dedicated datacenter of our own. This means that our next major expansion will likely ...
4
votes
6answers
611 views

Can QoS settings interfere with wireless printing? [closed]

This may seem like a rudimentary question, but I wasn't sure where else to ask it. I've set up some QoS rules on my router that give the highest priority to all traffic incoming and outgoing to my ...
17
votes
4answers
6k views

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 ...
10
votes
4answers
15k views

speed/duplex mismatch

How do mismatches occur; what is the impact of a mismatch on network connectivity; is resolution of mismatches really worth the effort; what are some ways to detect mismatches on a large scale?
21
votes
7answers
29k views

Introductory level explanation of VLANs

What's the basic use case(s) for VLANs? What are the basic design principles? I'm looking for something like a two paragraph executive summary style answer so I can determine if I need to learn ...
11
votes
3answers
2k views

Please help me understand this ADSL configuration

I've been working across many sites around the world with ADSL. The first output below is the one I've used many many times & I'm therefore most familiar with. It's from a site in the UK. ...
7
votes
2answers
522 views

Multi-tenancy TACACS server

Is it possible for Cisco ACS 5.4 (or any other version) to work in a multi-tenancy environment? I would like to have two ACS servers, one primary, one secondary, with completely different routing (...
7
votes
2answers
5k views

Why does 1000BASE-T need Auto-MDIX?

A 100BASE-TX PC interface sends out its frames on pins 1,2 and receives frames on pins 3,6. If we connect this PC's NIC with that of another PC we cannot use a straightout cable, because the frames ...
10
votes
3answers
5k views

Oversubscription in cisco 6500

What is oversubscription?When selecting a 16 port 10 gig blade for cisco 6500 , it says oversubscription as 4:1. What will happen if I populate all 16 ports, will some ports be blocking or dropping ...
1
vote
1answer
323 views

How do I obtain access to buy from Cisco directly? [closed]

I'm fairly new to the purchasing and licensing of new Cisco equipment. In the past, I have used eBay for all of my Cisco shopping needs. I know that I can purchase new equipment and licenses from ...
8
votes
2answers
2k views

Cisco 7600 q-in-q functionality on a Cisco 6500

Is it possible to make my existing 6509 switch function as a 7600 router? Even if it means purchasing a new sup or other inline card. I need certain router features, such as q-in-q tag termination. ...
13
votes
5answers
2k views

ASA 5550 - Reboot Worthwhile?

I've got an ASA 5550 that is performing loads and loads of operations (AnyConnect, NAT, ACL, RADIUS, etc, etc). It isn't particularly overloaded in terms of CPU & Memory, but it has an uptime of ...
5
votes
2answers
2k views

Cisco active/standby FWSM pair went active/active after switch upgrade

PROBLEM: Both FWSM in our core switches went active/active and protected subnets have partial accessibility. SETUP: We have 2 x Cisco Catalyst 6509 switches running IOS version 12.2(18). Each ...
6
votes
3answers
2k views

Is Riverbed Steelhead able to optimize print traffic between print server and a remote printer?

In the configuration for CIFS optimization, Steelhead offers an option to enable print optimization. From documentation I understood that when this option is checked the Steelhead will optimize the ...
6
votes
1answer
1k views

Daily, Weekly and Monthly Reports from Solarwinds?

I'm working with a Solar Winds NPM/NTA/IPAM golden-trio. I'd like to customize our reports to the point where I can received daily, weekly or monthly emails for various things - 95th percentile errors,...
10
votes
2answers
385 views

Will ASA 5540 support 3000 simultaneous IPsec connections?

As part of a new project, we have a requirement to terminate about 3000 IPsec connections on a Cisco ASA 5540 firewall. According to the specs, the maximum IPsec Peers this platform supports is 5000 ...
7
votes
2answers
15k views

How can I capture traffic on a Brocade XMR, MLX, CER or CES?

How can I perform a packet analysis on traffic flowing through a Brocade XMR, MLX, CER or CES without having to install a specific software on any of the remote endpoints ?
8
votes
6answers
408 views

What is the name of these broadband street cabinet connectors, and are they secure?

Can anyone help enlighten me, do these connectors have a formal name/standard? These are found in a street side ISP broadband cabinet for residential customers in the UK. Would I be correct in ...
14
votes
2answers
11k views

Why does “show interface” show “Last input never” when packets input is incrementing?

Why is it that when I perform a show interface command I see that Last input always shows never? FastEthernet1/31 is up, line protocol is up (connected) Hardware is C6k 100Mb 802.3, address is 000d....
47
votes
24answers
89k views

How can I see which switchports are not in use?

On a large Cisco Catalyst switch stack, almost all switchports are patched. I need to identify the ports, which are not in use, for connecting further devices. Following switchports, cabling, patch ...
15
votes
5answers
163k views

How can I reset a VPN tunnel on a Cisco ASA?

On a site-to-site VPN using a ASA 5520 and 5540, respectively, I noticed that from time to time traffic doesn't pass any more, sometimes just there's even missing traffic just for one specific traffic ...
12
votes
4answers
2k views

How can I formulate the communication latency in TCP/IP?

I have difficulty in deriving a mathematical model/equation to estimate the round trip latency between two nodes communicating using TCP/IP. The nodes are exchanging data based on HTTP protocol. In ...
23
votes
4answers
104k views

How can I capture traffic on Cisco IOS switches?

For investigating a problem in client to server communication, I need to capture packets for analysis. However it's not allowed to install a packet analyzer, such as Wireshark or tcpdump, on client or ...
13
votes
1answer
13k views

What is the 5 level QoS model (through config example)?

I have heard people stating that their network "operates a 5 level (or layer) QoS model" Sometimes they also mention a 7 level QoS model. Can anyone provide me with a Cisco IOS config example of ...
17
votes
4answers
7k views

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 ...
6
votes
2answers
3k views

Juniper SRX240 Clustering - Policy out of sync

I have two Juniper SRX240's in a cluster. After re-ordering some security policies on the primary device and committing them ok I now can not make any other changes without the warning error: ...
12
votes
1answer
2k views

ASA5505 and IPv6 over a PPPoE Link

I see a lot of conflicting information about whether or not a Cisco ASA (5505 in this case) can use IPv6 over a PPPoE connection. I see official Cisco documentation making it look easy, but I see ...
12
votes
1answer
14k views

Cisco ISR G2 encrypted bandwidth restriction?

I have been having complaints of a "slow connection" from several new remote sites. The sites are connected via an MPLS L3VPN service into Cisco 2921's, and we are using Cisco GET-VPN to encrypt ...
10
votes
1answer
4k views

Configuring HSRP on Nexus OS

How do you configure HSRP on a Nexus 7000 series switch? I know in IOS the commands are in the interface configuration, for example: switch-a#config t switch-a(config)#interface g1/0/1 switch-a(...
7
votes
1answer
2k views

What are some workarounds / fixes for UTM/IDP on Junos 12.1X44-D10.4 for SRX Series branch devices?

The JNCIP / JNCIE-SEC latest courses use 12.1X44-D10.4 as the recommended Junos version. I setup a 30-day evaluation on my home SRX device to study JIPS, based on 12.1. At this point, I'm guessing ...
14
votes
7answers
8k views

How to connect 5 different networks together?

I have a network consisting of three servers in a data center, all of which are connected to each other via a switch. In addition to this I need this network to access 4 additional networks, most of ...
37
votes
8answers
27k views

How would a router with /32 WAN subnet mask communicate with the rest of the Internet?

I'm studying networking and one of the most basic things I've been told countless times is that computers can't communicate outside of their own subnet. On the other hand, by looking at some ADSL ...
10
votes
1answer
3k views

Cisco WLC External WebAuth Apparent Random Behavior

On Cisco 5508 v7.2.103.0, I have a couple of WLANs configured. Call them ABC and XYZ for the sake of this question. ABC uses 802.1X and gets a splash page redirect URL pushed down. XYZ uses PSK and ...
24
votes
10answers
233k views

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

On a Cisco Catalyst switch, I need to find what port an end device is connected to. I have the IP address/host name. How do I quickly find the port?
13
votes
4answers
6k views

Hardware tap vs port mirroring - Any limitations?

I predominantly work in a Cisco environment and contemplating buying a network tap device for use with Wireshark. Can anyone provide the pros and cons from their experience between using network taps ...
10
votes
2answers
2k views

Why does my Cisco 6509 BGP table use two entries in my TCAM?

I have a problem on my Cisco 6509, each entry in my BGP table occupies two entries in the TCAM. If I show capacity forwarding, I see MPLS entries in L3 forwarding resources. But, I do not use MPLS on ...
6
votes
3answers
683 views

Is there a way to test TRILL in a virtual lab?

I don't have access to devices to run TRILL for testing and learning purposes, so is there a way to set-up a virtualized lab to try it ? What would be the virtualisation system, the vendor, the ...
10
votes
4answers
1k views

Should spanning tree path costs match on a physical link?

While working on a set of switches I noticed that the spanning tree path costs aren't set up to match on opposite sides of the same physical link. For some reason that doesn't look right to me. ...

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