Question on ARP table on 3750 switch

Hi,
So I have a cisco 3750 switch directly connected to a 2851 router gig 0/0 interface.
Should the show arp command on the switch show an entry for the IP and mac address of the routers gig 0/0 interface?
I dont see one in there now and was just wondering.
Connectivity between the switch and router work fine right now.
thanks

HI Bill,
if u can ping from Swicth ro router,,,,then please check with this command: sh ip arp.
Just for Info;
To be able to ARP a device, you must have an interface (SVI) on that switch on that network. To ARP a device you must have an interface with a layer 3 IP on the same layer 2 vlan.
You will need to connect to a switch that has an interface on that vlan on it. I would traceroute to the host, and hopefully the next to last hop is the layer 3 switch, or if it's a router, connect to it and do a show cdp neighbors and see if you can find the switch that way. (If you do connect to the router, you'll find the ARP entries there, if it's a layer 3 switch, then it's both a router and switch in one box)
"sh mac address-table". This will give which MAC is connected to which port.
"sh ip device tracking interface gigabitEthernet ". This will give which IP is connectd to a port.
"sh ip arp" will give you a IP to MAC table
Regards
Dont forget to rate helpful posts.

Similar Messages

LAN - ARP Table

Hello,
I'm not sure if someone has come across this before. But they might enlighten me.
Under what circumstances would you see ARP enteries on a switch for subnets out side of the local subnet?
Example 2 switches back to back everything in default vlan 1. These uplink to a pair of routers running HSRP.
I would expect to see x.x.x.200 /24
arp enteries for devices on the switches
but not addresses outside of this range.
Any input appreciated.
Thank you.

Suppose you are talking layer2 switches like the 2950 series?
First of all, this has nothing to do with the switching process on the access ports. The arp table on a switch is only used for the IP management interface. ARP entries will appear for anything that you contact from the console.
Typically anything beyond your local subnet is covered by a default gateway but when the switch is using proxy-arp for address resolution you can see anything on your network.
Regards,
Leo

Grab ARP Table via SNMP on HP v1910 switch?

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Hi: You may also want to post your question on the HP Enterprise Business Community support forum -- Procurve Switches section. http://h30499.www3.hp.com/t5/ProCurve-ProVision-Based/bd-p/switching-e-series-forum#.VaKx2ofbLGg

QoS Questions for 3750 Switches

2x3750 switches are stacked and we are trying to simulate traffic congestion at the UTP ports by using Smartbit 6000C. The objective of the test is to see if the QoS setting works in reality even though we see from Wireshark that the packets are marked with DSCP for voice traffic.
Setup is as follows :
Smartbit<->Avaya IP Phone<->3750 switches<->6509 switch.
Please note that the configuration is set on the 3750 switch port as well as trusted on the Cat 6 switch port. However, when I set to continuous traffic with byte size of 64. Even though its a 100Mbps port, the Avaya IP Phone is already acting weird with hanged symptom. Just side note is that performing "show mls qos inter gi2/0/7 statistic" shows that data and voice traffic are marked on the different priority which seemed correct.
1) Is this the right way to test? If not, what should be the correct way?
2) The port that's connected to Smartbit is configured and it seemed that with the continuous traffic, even other IP Phones are hanged even though I have set Smartbit to hit on the IP address of the CAT6 Switch port. This is not normal right as this is supposed to be unicast traffic. Any idea what could be the reason?

Hello Brandon,
I understand your concern and how you want to test, but with the VoIP services you need to understand that there are 2 points (telephones if you want) involved. Your local one, where you might have taken all the necessary steps to protect and prioritize your voice traffic, and the oposite end which also need to have the voice packets prioritized.
Now, from your description, I understand that the packets (voice and data) marked correctly (I believe on C3750), but that's not enough. You need to use CBWFQ together with LLQ to give priority to the Voice traffic over data in case of congestion. Do you have such configuration? Can you show us some excerpt from it?
Next, during the testing, you said that your phone hang-up...where you in a call?
To respond to your questions:
1. The start is ok, but we need more details. You are pushing traffic from Smarbit, this is your local end, but where is the traffic pushed to (remote end), who is receiving the traffic?
2. In theory, you shouldn't have any impact over voice if links are 100Mbit, only if you have such a power packet generator that could fill 100Mbit. What do you mean by "This is not normal right as this is supposed to be unicast traffic"? VoIP is also unicast traffic...
I can see that you are determined to solve this issue, and this is OK as it will help you back with gained knowledge, but I have to warn you that troubleshooting QoS / Voice related problems may be more tricky than you think, as it will involve a strong know-how in these areas.
We will help, but you have to come back with more precise details.
Good luck!
Calin

Arp table and mac table in cisco 4503 switch

Hi all,
I have a problem with 4503 switch
I have 7 highend servers in my lan i.e 5hp and 2dell servers.
Each server has 4 network interface cards(1g). so 7*4=28 ports.
I have create vlan 70, ip add is 10.70.70.1
I have assign ip address to servers like
first server         10.70.70.2, 10.70.70.12,
Second server   10.70.70.3, 10.70.70.13,
Third server        10.70.70.4, 10.70.70.14,
fourth Server       10.70.70.5, 10.70.70.15, 10.70.70.25, 10.70.70.35
fifth server           10.70.70.6, 10.70.70.16, 10.70.70.26, 10.70.70.36
sixth server          10.70.70.7, 10.70.70.17, 10.70.70.27, 10.70.70.37
seventh server      10.70.70.8, 10.70.70.18, 10.70.70.28, 10.70.70.38
The problem is in four interfaces each server, only one or two interfaces are pinging, remaining interface are not pinging.
for example in the first server i can able to ping 10.70.70.12- macid 60eb.69d2.a2aa
                                            i can't able to ping 10.70.70.2- macid 60eb.69d2.a2ab
second, fourth, fifth, sixth, and seventh continiously pinging successfully.
for example in fourth server i can able to ping 10.70.70.5 macid -b499.bafe.9c98
                                         i can able to ping 10.70.70.15 macid-b499.bafe.9c98
                                         i can able to ping 10.70.70.25 macid-b499.bafe.9c98
                                         i can able to ping 10.70.70.35 macid-b499.bafe.9c98
now you understand what is the problem, which server i am not getting pinging that arp table shows each interface separte mac address
                                                   which server i am getting pinging that arp table shows each interface bind with same mac address(dynamically)
Please give me the solution

Hi,
I Think you need to do Teaming on the servers.
++ configure etherchannel between switch and the server.
configuring etherchannel b/w 4503 and server:
================================
http://www.cisco.com/en/US/tech/tk389/tk213/technologies_configuration_example09186a008089a821.shtml
Sample NIC Teaming - HP NICs with Cisco Switches (EtherChannel) :
==============================================
http://support.citrix.com/article/CTX434260
There are several NIC teaming technologies available today from switch vendors. Cisco uses the term “EtherChannel.” Various switch vendors use various terms, and these may or may not provide the same exact functionality. Use of EtherChannel technology requires support from the server hardware vendor, NIC vendor, and Layer-2 switch vendor.
Hope this helps
Cheers
Somu
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Sending Ciscowrks device credential Verification Job alters the device ARP table.

Hi:
I send a Device credential verification Job to two different devices , a Cisco 3750 and a blade switch WS-CBS3120. I configured SNMP write access to the switches. The SNMP write access in either SNMP v1 or SNMP V3 , tried both.
The job is send from the Ciscoworks server.
Once the job has completed, I do a show ip arp on the device and find a new entry with the IP address of the Ciscoworks Server and the mac-address of the L2 next hop.
We would not have noticed this behavior had it not been that in the case that the switch next hop is an HSRP vlan on a nexus , the ARP entry entered into the switch is incorrect, and from then on the switch loses connection to Ciscoworks.
The Mac-address that is entered by Ciscoworks , in the case of nexus is a statice mac defined on the Nexus for the Vlan in question , but it is NOT the HSRP default gateway MAC address. Therefore we lose connection between the switch and Ciscoworks. One has to manually clear the ARP table inorder to again reach the Ciscoworks.
Questions:
1. Why does Ciscoworks insist on changing the ARP table?
2. Is this ARP entry aged out or is it permeant as would an ARP entry which is entered through CLI be permeant ?
3. In the case of the Nexus connection, this ARP entry does not allow Ciscoworks and the device to communicate. This is not productive!
Has any one come across this situation ? Any known fixes, workarround? I was not able to find a word about this on Cisco's site.
Our Ciscoworks is at the following levels:
CW Common services    3.3.0
LMS portal                    1.2.0
CW Assistent                1.2.0
RME                             4.3.1
Device fault manager      3.2.0
IPM                              4.2.1
Cisco View                    6.1.9
campus Manager            5.2.1
thanks   for any help
Mickey

CiscoWorks does not change the ARP table, at least not overtly. A credential verification job will do the following things depending on what protocols are selected to test:
SNMP RO : Fetches sysLocation.0
SNMP RW : Sets sysLocation.0 to the value currently stored in sysLocation.0
Telnet : Logs in using DCR username and password
SSH : Logs in using DCR username and password
Enable : Enters enable mode and verifies privilege level 15
If one of these things are causing the ARP table to change, then there is something fishy in the device or network configuration. I've never heard of such behavior relating to CiscoWorks before.

Host not showing up in ARP table

Hi,
I am having an interesting/weird problem with one of my Catalyst 6509 switches.
The setup is as follows:
HostA - Switch1 - Switch2 - HostB
There is routing in place for HostA to reach HostB and vica versa.
I am testing this using ICMP. There is nothing blocking ICMP traffic on any of the devices.
Problem in question: I can only ping HostB from HostA (or Switch1) if HostB is found in the ARP table of Switch2. Pretty normal you might say since we need Switch2 to route/switch the packet to HostB and that will of course only happen if the ARP table is populated.
But what happens is the following:
I ping from HostA to HostB. It fails. I check Switch2 and I see that HostB is nowhere to be found in its ARP table.
Next I ping HostB from Switch2 (5 packets). First packet fails, last 4 I get a reply. I check and see that now HostB is to be found in the ARP table of Switch2.
Now I ping HostB from HostA and it works fine.
This behaviour is happening for all hosts in the subnet (VLAN) of HostB. I cannot reach them until I ping them from Switch2, after which they're in the ARP table and everything works.
Maybe it something different than the ARP table not being populated all together, but that is for now all I noticed. Does this problem ring a bell with anyone. And is there a fix?
It looks to me like Switch2 is malfunctioning, although I have no idea what is. Furthermore this apears to be working ok for a lot (read: all) of the other VLANS on Switch2.
Anyway. I'd love some help in troubleshooting this one.
kind regards,
Kevin

This goes back to the way switches (or bridges) work. They have to see a frame from an end device to know its MAC address and once they see it they add an entry in their CAM (or MAC) table. The entry basically tells the switch that a specific MAC is reachable via a particular port and this is meant to prevent subsequent flooding of unicast frames. In short an end device needs to send at least one frame for the switch to 'see' it. Another point to remember is that each entry in the CAM table has an age associated with it and if a switch does not see subsequent frames from that host it will age out the entry and start flooding all frames destined to this MAC address until it is learnt again (and learning is done only when the owner of the MAC starts to communicate again).
Kevin,
Can you please explain your topology in a bit more detail? I am looking for information like what is the default gateway of each VLAN, how are the VLANs spread across the two switches, any HSRP configurations and if yes who is the active for what VLAN, routing between switches, etc. This will help us troubleshoot the problem in a more effective manner.

Sometimes Local Address not in ARP table and Ping fails (network problem?)

I see something like this on our network a couple of times a week.
The same replies have been received from different hosts.
ping fails
local subnet machine is not in arp table
ping fails
local subnet machine is not in arp table
traceroute may or maynot succeed
If traceroute succeeds an entry is in the arp table
if traceroute fails no entry will be in the arp table.
A netstat -s, ont the local host, doesn't show any thing strange except that udpNoPorts=10844982 (Unfortunately I don't know what udpNoPorts is)
The remote host IS UP.
Does anyone have an idea as to why this is happening?
Can our 100mb network, which is not that busy, be loosing that many ICMP or ARP messages?
This is a problem because I'm the guy getting paged if a system is down.
Local host is Solaris 7 on same subnet at IP 168.173.8.8
Remote hosts are usually NT boxes.
/usr/sbin/ping -svR stpaul_web2 56 3
----stpaul_web2.agribank.com PING Statistics----
3 packets transmitted, 0 packets received, 100% packet loss
/usr/sbin/arp stpaul_web2
stpaul_web2 (168.173.8.143) -- no entry
/usr/sbin/ping -svR stpaul_web2 56 3
----stpaul_web2.agribank.com PING Statistics----
3 packets transmitted, 0 packets received, 100% packet loss
/usr/sbin/arp stpaul_web2
stpaul_web2 (168.173.8.143) -- no entry
/usr/sbin/traceroute stpaul_web2
1 stpaul_web2.AGRIBANK.COM (168.173.8.143) 2995.868 ms 0.231 ms 0.211 ms
/usr/sbin/arp stpaul_web2
stpaul_web2 (168.173.8.143) at 0:1:2:cc:a3:51
Any help is greatly appreciated.
Ks

Hi,
I Think you need to do Teaming on the servers.
++ configure etherchannel between switch and the server.
configuring etherchannel b/w 4503 and server:
================================
http://www.cisco.com/en/US/tech/tk389/tk213/technologies_configuration_example09186a008089a821.shtml
Sample NIC Teaming - HP NICs with Cisco Switches (EtherChannel) :
==============================================
http://support.citrix.com/article/CTX434260
There are several NIC teaming technologies available today from switch vendors. Cisco uses the term “EtherChannel.” Various switch vendors use various terms, and these may or may not provide the same exact functionality. Use of EtherChannel technology requires support from the server hardware vendor, NIC vendor, and Layer-2 switch vendor.
Hope this helps
Cheers
Somu
Rate helpful posts

ARP table not populating mac address for previously reachable IP address

Router has been online and working fine with one BGP neighbor for almost 2 years and no downtime. 2 weeks ago, added a 2nd BGP peer. Everything worked fine for 2 weeks, then all of a sudden yesterday the 2nd BGP peer is disconnected and does not come back. ISP checks and sees everything looks fine on their end. We cannot even ping each other now.
Upon investigation, the ARP table is not even populating the MAC address for the BGP peer IP anymore (same local subnet). Stays "incomplete" in the table no matter what we do, including clearing arp table, changing IP address, etc.
Plug a laptop directly into the 2nd BGP peer FE port and replicate the IP addressing. Laptop cannot ping Router, but Router CAN ping laptop. Check ARP table, but STILL no mac address assigned and now not even the ARP table showing "incomplete".
Thinking it could be the FE interface, switch to the 2nd FE interface and perform same laptop test, this time with arbitrary IP addressing. Now cannot ping each other, no MAC in ARP table.
End up rebooting the router and lo-and-behold, everything is working normally again. 2nd BGP peer peers up instantly.
I should also mention that the 1st BGP peer worked flawlessly throughout, taking all the Internet load and having no issues throughout.
Also, the FE ports for the 2nd BGP peer are on an HWIC FE card plugged into the router. The 1st BGP peer is plugged into the built-in GE interface. 2901 running: c2900-universalk9-mz.SPA.151-4.M4.bin
Lastly, no router resource issues, no error messages, no logs. Just the BGP peer disconnecting.
I have never, in 20 years working with Cisco routers seen something like this before. This is the most fundamental aspect of IP and Ethernet that was not working.
Has anyone ever seen this behavior before??
Here is the router config (IP's changed):
version 15.1
service timestamps debug datetime msec localtime show-timezone
service timestamps log datetime msec localtime show-timezone
service password-encryption
service internal
service sequence-numbers
boot-start-marker
boot-end-marker
logging buffered 150000
aaa new-model
aaa authentication login LAUTHEN local
aaa authentication login TAUTHEN local group tacacs+ enable
aaa authorization console
aaa authorization exec LAUTHOR local if-authenticated
aaa authorization exec TAUTHOR local group tacacs+ if-authenticated
aaa session-id common
clock timezone PST -8 0
clock summer-time PDT recurring
no ipv6 cef
no ip source-route
ip cef
no ip domain lookup
multilink bundle-name authenticated
username ubiadmin privilege 15 secret 4 .JbeuWXuZvchrG0OL.5BftFtqrrEyxcnVHn5rIuCnTk
username umitsnoc01 privilege 15 secret 4 cUmoRUjey9O1x.wk9S.kleX.iAAhCwihupr6Z98p6OA
redundancy
ip ssh version 2
track 1 interface GigabitEthernet0/0 line-protocol
class-map match-any AutoQoS-VoIP-RTP-Trust
match access-group name SIP-Media-INBOUND
class-map match-any AutoQoS-VoIP-Control-Trust
match ip dscp cs3
match ip dscp af31
class-map match-any Customer-Voice
match access-group name Customer-VPNs
class-map match-any media
match access-group name SIP-Media
class-map match-any signaling
match access-group name SIP-Signaling
policy-map AutoQoS-Policy-Trust
class AutoQoS-VoIP-RTP-Trust
priority percent 70
class AutoQoS-VoIP-Control-Trust
bandwidth percent 5
class class-default
fair-queue
policy-map queue
class signaling
bandwidth percent 5
class media
priority percent 50
class Customer-Voice
priority percent 40
class class-default
fair-queue
policy-map shape
class class-default
shape average 10000000
service-policy queue
interface Embedded-Service-Engine0/0
no ip address
shutdown
interface GigabitEthernet0/0
description BGP Peer 1
ip address 2.2.2.2 255.255.255.252
no ip redirects
ip flow ingress
ip flow egress
duplex auto
speed auto
service-policy output shape
interface GigabitEthernet0/1
description LAN
ip address 1.2.3.4 255.255.255.0
no ip redirects
ip flow ingress
ip flow egress
standby 255 ip 1.2.3.1
standby 255 priority 105
standby 255 preempt
standby 255 mac-address 1a2b.3c4d.5e6f
standby 255 track 1 decrement 10
duplex auto
speed auto
service-policy output AutoQoS-Policy-Trust
interface FastEthernet0/0/0
description BGP Peer 2
ip address 1.1.1.1 255.255.255.252
ip flow ingress
ip flow egress
duplex full
speed 100
service-policy output shape
interface FastEthernet0/0/1
no ip address
shutdown
duplex auto
speed auto
router bgp 7777
bgp router-id 2.2.2.2
bgp log-neighbor-changes
network 1.2.3.0 mask 255.255.255.0
neighbor 1.1.1.2 remote-as 5555
neighbor 1.1.1.2 update-source FastEthernet0/0/0
neighbor 1.1.1.2 prefix-list L3-DEFGW in
neighbor 1.1.1.2 route-map L3-LPREF-IN in
neighbor 2.2.2.1 remote-as 6666
neighbor 2.2.2.1 ebgp-multihop 2
neighbor 2.2.2.1 update-source GigabitEthernet0/0
neighbor 2.2.2.1 send-community
neighbor 2.2.2.1 prefix-list COLO-DEFGW in
neighbor 2.2.2.1 route-map COLO-LPREF-IN in
neighbor 2.2.2.1 route-map COLO-OUT out
ip forward-protocol nd
ip bgp-community new-format
ip as-path access-list 5 permit _5555_
ip as-path access-list 5 deny .*
ip as-path access-list 10 permit ^6666$
no ip http server
no ip http secure-server
ip flow-top-talkers
top 50
sort-by bytes
ip route 0.0.0.0 0.0.0.0 1.1.1.2 254 name L3
ip route 0.0.0.0 0.0.0.0 2.2.2.1 255 name COLO1
ip route 10.0.0.0 255.0.0.0 10.10.10.10 name FW_OUTSIDE
ip tacacs source-interface GigabitEthernet0/1
ip access-list standard SNMP_SOURCES
permit 12.12.12.0 0.0.0.255
deny any log
ip prefix-list L3-DEFGW seq 5 permit 0.0.0.0/0
ip prefix-list COLO-DEFGW seq 5 permit 0.0.0.0/0
ip prefix-list COLO-LPREF-OUT seq 5 permit 1.2.3.0/24
route-map COLO-LPREF-IN permit 5
match as-path 5
set local-preference 250
route-map COLO-LPREF-IN permit 10
set local-preference 150
route-map COLO-LPREF-IN permit 20
route-map COLO-OUT permit 10
match ip address prefix-list COLO-LPREF-OUT
set as-path prepend 7777 7777 7777
set community 29795:1004
route-map COLO-OUT permit 20
route-map L3-LPREF-IN permit 10
match as-path 10
set local-preference 200
route-map L3-LPREF-IN permit 20
set local-preference 150
snmp-server enable traps snmp authentication linkdown linkup coldstart warmstart
snmp-server enable traps vrrp
snmp-server enable traps flowmon
snmp-server enable traps transceiver all
snmp-server enable traps ds1
snmp-server enable traps call-home message-send-fail server-fail
snmp-server enable traps tty
snmp-server enable traps license
snmp-server enable traps envmon
snmp-server enable traps ethernet cfm cc mep-up mep-down cross-connect loop config
snmp-server enable traps ethernet cfm crosscheck mep-missing mep-unknown service-up
snmp-server enable traps flash insertion removal
snmp-server enable traps mac-notification
snmp-server enable traps aaa_server
snmp-server enable traps cef resource-failure peer-state-change peer-fib-state-change inconsistency
snmp-server enable traps memory bufferpeak
snmp-server enable traps config-copy
snmp-server enable traps config
snmp-server enable traps config-ctid
snmp-server enable traps event-manager
snmp-server enable traps hsrp
snmp-server enable traps cpu threshold
snmp-server enable traps rsvp
snmp-server enable traps syslog
snmp-server enable traps vtp
snmp-server enable traps ipsla

When you were checking the ARP table was there an entry for Fast0/0/0?
HTH
Rick

Gratuitous ARPs do not populate the router ARP Table

Hello,
In order to debug an ARP problem in a Firewall cluster environment, I connected a one-armed router on the public VLAN of the firewall cluster, in order to observe the ARP cache behaviour during a switchover. I configured a loopback interface on this router and a default route to this loopback interface to simulate a real router.
When a switchover occurs between firewall cluster members, the active member sends Gratuitous ARPs for all NATed IP addresses. In my environment, I have 110 NATed addresses configured on the firewall.
By launching a "debug arp" on the one armed router, I clearly see all 110 gratuitous ARPs arriving on the router, but the ARP cache of the router is NOT populated with the 110 entries...
Note : The command is configured on the one armed router :
Router(config)# ip arp gratuitous local
What can be the problem ? Is there any condition for a router to accept Gratuitous ARPs ?
Thank you for any help
Yves

Hi
Gratuitous arp is used when a host wants to inform the switch that the mac-address has changed eg.
You have a cluster which has redundant connections and an IP to mac-address mapping. If the active NIC fails the IP address is moved across to the standby NIC but the standby NIC has a different mac-address. So the cluster sends out a gratuitous arp which informs the switch of the new IP to mac-address mapping.
The reason you might not want to allow gratuitous arp is that you might not want your switch updating it's arp table based on annoucements from devices on the LAN as you could very easily spoof mac-addresses and corrupt the arp cache.
HTH
Jon

Esw-540-48 - direclty connected to port 34, still no MAC in ARP table

Hi all,
I have a ESW-540-48 with firmware 2.1.21 (latest)
I have the strangest problem: I can 't find the MAC address of a computer plugged directly on the switch in the ARP table.
I'm trying to search by MAC address, and also by port .
If I reboot the switch, it does work as expected.
Do you think it is software related, and in this case is there anything planned to solve this problem ?
Or maybe I should just replace my hardware ?
Thanks

Hi Firco, it may be possible it is a smart port issue. The ESW switches are very particular to use the correct smart port roles for the connecting devices. I don't think a hardware replacement is warranted unless the given ports absolutely failed to forward.
As a secondary thought, it could also be a spanning tree issue. Ensure you're using RSTP and/or the host ports have port fast enabled. If using classic spanning tree it takes nearly a minute for a port to go to forwarding state. You can disable spanning tree on the port for testing to quickly rule that out.

Connection of LC/APC fiber patch cords to Cisco Catalyst 6500 $ Cisco Access 3750 Switches

I have an LC/APC fiber patch cord infrastructure and I want to connect it to Cisco Catalyst 6500 & Cisco Access 3750 Switches. what type of transceiver should be used?
I read a note on Cisco website stating the following for Cisco SFP+ transceivers:
Note: "Only connections with patch cords with PC or UPC connectors are supported. Patch cords with APC connectors are not supported. All cables and cable assemblies used must be compliant with the standards specified in the standards section"

Thank you, but my question is that I have a single mode fiber patch cord with LC/APC connector while cisco stating a note that only use LC/PC or LC/UPC type of connectors with SFP+ transceiver.
So what type of transceiver should I use to connect LC/APC patch cord to cisco switches? Is there another type or SFP+ still can be used?

3750G won't "age out" old arp table entries

WS-C3750G-24TS running
12.2(20)SE4, RELEASE SOFTWARE (fc1).
sho mac-address-table aging-time
Vlan Aging Time
253 300
252 300
254 300
255 300
1 300
251 300
The aging is not working. I can failover some devices I have and the mac-address of the old device associated the the IP never ages out. "Clear arp" makes the standby unit respond to pings and connectivity to the standby unit is 100% after the "clear arp".
Showing the arp cache, I can see the IP associated with the old mac-address and the "age" keeps increasing, not decreasing with the old mac-address.
It also doesn't matter if the Primary unit has been rebooted, switch keeps the old mac-address associated the Primary unit.
Suggestions?

I think permanent entry should have been made into the arp cache using the "arp ip-address hardware-address type" command.
To remove this arp entry, you can try "clear arp-cache".This will delete all dynamic entries from the ARP table.
for more details, refer the following page:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_command_reference_chapter09186a00800ca5b0.html#1017562

Question related to SFP, Fiber, and switches model Compatibility for Gigs Connections

Hi everyone,
I am in the middle of a project where we are receiving a 2gig Internet connection from a service provider. I need to connect this to a switch , my question is related to what sfp, switch would be the most compatible. I was thinking about a 3750 switch with sfp modules, but i am not sure if a SFP 1000 sx is enough as we are receiving a 2 gig connection via fiber then I would need to use a 10G module, with 10G sfps... mm well i am very confuse... can anyone help me please in your experience with a similar situation
Thanks.

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A "2 gig" connection might mean a 10g logically limited to 2g, or it might mean the full duplex capacity of a gig link.
The SFP+ ports on 10g 3750X modules will support either a gig or 10g transceiver. The SPF ports, on either 10g or gig modules will only support gig.

WOL and ARP Tables in BT Home Hub 2

Hi,
I have noticed several posts on the forum around the matter of WOL and also using port-forwarding to games devices but have not seen any definitive answer to my question.
I am wanting to use WOL in order to access my home PC from a netbook when away from home without having to leave it on all the time.
I have my PC set up to WOL using WOL Magic Packet Sender and DynDNS. This all works fine until the Home Hub refreshes its ARP table and it no longer finds my PC.
I have managed to set things up so I have a telnet connection to the hub and can run arp -a to see the existing entries. However, whenever I try to do an arp -s inet_addr mac_addr it comes up with Segmentation Error. I have tried deleting all reference to my PC and adding the static entry from my netbook but this gives the same result. I have tried both with DHCP and static addresses in the PC.
Does anyone know if it is possible to set up a permanent ARP entry in the Home Hub, please? BT online support say they are not trained in such matters (after disconnecting me twice) and suggest phoning in for chargeable help.
Cheers,
Joan

I'd like to do this too. I had it set on my previous ISP's Thompson 585v7 router, which is hardly cutting edge so I'd hope it's possible with the Home Hub.

Question on ARP table on 3750 switch

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