Switching

Hello all,

I connected two PCs on the same access switch Ex2200 on the same Vlan (Vlan-ID 2 ) for testing purposes. Since they are connected on the same VLAN, they should be able to reach each other. However, that's not the case.

PC 1 IP: 10.10.10.1---GE0/0/0

en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500

options=10b<RXCSUM,TXCSUM,VLAN_HWTAGGING,AV>

ether 98:5a:eb:e2:22:9e

inet6 fe80::c2e:c452:ea33:f26f%en0 prefixlen 64 secured scopeid 0x7

inet 10.10.10.1 netmask 0xffffff00 broadcast 10.10.10.255

nd6 options=201<PERFORMNUD,DAD>

media: autoselect (1000baseT <full-duplex,flow-control>)

status: active

PC2 IP 10.10.10.2--GE0/0/1

Ethernet adapter Ethernet:

Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Realtek PCIe GbE Family Controller
Physical Address. . . . . . . . . : A0-1E-0B-05-0B-0B
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::b083:3801:4eb5:6b4b%11(Preferred)
IPv4 Address. . . . . . . . . . . : 10.10.10.2(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . :

Wireless adapter was connected for this PC and it has its own default gateway

I see the mac addresses learned on the switch

root@juniper-lab> show ethernet-switching table
Ethernet-switching table: 3 entries, 2 learned, 0 persistent entries
VLAN MAC address Type Age Interfaces
test * Flood - All-members
test 98:5a:eb:e2:22:9e Learn 0 ge-0/0/0.0
test a0:1e:0b:05:0b:0b Learn 39 ge-0/0/1.0

{master:0}
root@juniper-lab> show vlans
Name Tag Interfaces
default
ge-0/0/2.0, ge-0/0/3.0, ge-0/0/4.0, ge-0/0/5.0,
ge-0/0/6.0, ge-0/0/7.0, ge-0/0/8.0, ge-0/0/9.0,
ge-0/0/13.0, ge-0/0/14.0, ge-0/0/15.0, ge-0/0/16.0,
ge-0/0/17.0, ge-0/0/18.0, ge-0/0/19.0, ge-0/0/20.0,
ge-0/0/21.0, ge-0/0/22.0, ge-0/0/23.0
test 2
ae0.0, ge-0/0/0.0*, ge-0/0/1.0*, ge-0/0/12.0

{master:0}

root@juniper-lab> show configuration vlans
test {
vlan-id 2;
}

{master:0}

PC 2 

I don't see an arp entry for its destination

C:\Users\Computer>arp -a

Interface: 10.10.10.2 --- 0xb
Internet Address Physical Address Type
10.10.10.255 ff-ff-ff-ff-ff-ff static
224.0.0.22 01-00-5e-00-00-16 static
224.0.0.251 01-00-5e-00-00-fb static
224.0.0.252 01-00-5e-00-00-fc static
239.255.255.250 01-00-5e-7f-ff-fa static

Interface: 192.168.2.10 --- 0x10
Internet Address Physical Address Type
192.168.2.1 ac-3b-77-a7-16-28 dynamic
192.168.2.50 b2-95-75-6a-52-ff dynamic
192.168.2.101 b2-95-75-ec-65-db dynamic
192.168.2.103 c0-ce-cd-ec-65-db dynamic
192.168.2.104 80-2b-f9-24-80-65 dynamic
192.168.2.110 f0-5c-77-28-d8-0d dynamic
192.168.2.111 a4-77-33-b9-18-60 dynamic
192.168.2.122 18-56-80-9a-e2-96 dynamic
192.168.2.200 b2-95-75-0b-ef-92 dynamic
192.168.2.255 ff-ff-ff-ff-ff-ff static
224.0.0.22 01-00-5e-00-00-16 static
224.0.0.251 01-00-5e-00-00-fb static
224.0.0.252 01-00-5e-00-00-fc static
239.255.255.250 01-00-5e-7f-ff-fa static
255.255.255.255 ff-ff-ff-ff-ff-ff static

PC1

I see an arp entry that is incomplete or sometimes  shows this a0:1e:b:5:b:b, it doesnt show zeros
MacBook-Pro:~ sid$ arp -a
? (10.10.10.1) at 98:5a:eb:e2:22:9e on en0 ifscope permanent [ethernet]
? (10.10.10.2) at (incomplete) on en0 ifscope [ethernet]

What am I missing here ?. How do I fix this?

Hello Junipersid,

I believe you have you configured the interfaces ge-0/0/0 and ge-0/0/1 as access ports for vlan-id 2 as below.

[edit interfaces ge-0/0/0]
unit 0 {
family bridge {
interface-mode access;
vlan-id 2;
}
}

Have you checked for any firewall installed on the PCs that is blocking traffic?

I found out the cause of the issue. It's one of the test PCs Ethernet port that's problematic. As soon as I used different PC flawlessly.

Hi junipersid, 

Very glad the issue is solved, if you think my post help to resolve your issue, please mark my answer as solved 😉 , thank you.

Regards, 

Franky

Hi junipersid, 

Since you are using MAC you can use tcpdump in your terminal and see if the ARP request/reply are ingressing/engress your port and see where is getting lost or wireshark for your Windows PC, "incomplete" means that is waiting an ARP reply.

-Does "show ethernet-switching interface ge-0/0/0 and show ethernet-switching interface" shows in forwarding state?

-Try other ports and see if that works or use another Vlan.

-if you connect your Windows PC to your MAC with ethernet cable, does it work?

-What is your configuration for those ports and what version you are running on EX? 

-try clearing the arp on both machines...

-Have you try disabling and enabling the switchport ? set interface ge-0/0/0 disable , set interface ge-0/0/1 disable and then rollback ? 

-Do you see any interface on the switch?

Thank you, 

Franky

Yes performed packet captures on the port connected (on Junos switch)to the PC2 windows machine. I didn't see any packets at all, not even arp. I found out the cause of the issue. It's one of the test PCs Ethernet port that's problematic. As soon as I used different PC , things started working flawlessly. Its weird though.