Routing

Hi, 

I would like to ask if anyone can suggest a working solution.

I got 2 routing egines in 4300 VC connected to a router via Shaper and Riverbed WAN optimalization device. Because of the RB device I need to use two different subnets between the VC switch and router. I am running eBGP on these two subnets. For BGP sessions Router's IPs are on interfaces and switch IPs are on IRB interfaces, Problem I am facing is that the router sees both IP addresses from VC switch with the same MAC address, even they are from different vlan/irb. How can I fix this?

thx

---------------------|     |----------------  |     |-------------|     | ------------------------------|-

ex4300 node0 | -- | RB(inpath0) | -- |SHAPER | -- | Cisco router (int gi0/0) |

ex4300 node1 | -- | RB(inpath1) | -- |SHAPER | --  | Cisco router (int gi0/1) |

---------------------|    | ----------------  |     |-------------|     |--------------------------------|

Hello,

There are at least 2 ways to do it:

1/ in JUNOS 13.3, MAC address per IRB unit is user-configurable, at least on MX. Never tried it on EX4300, but give this a try:

set interfaces irb unit X mac 02:02:02:00:00:00

2/ if the above fails, make one IRB unit a VRRP master with own IP:

set interfaces irb unit X family inet address 198.18.1.1/30 vrrp-group 10 virtual-address 198.18.1.1
set interfaces irb unit X family inet address 198.18.1.1/30 vrrp-group 10 priority 255
set interfaces irb unit X family inet address 198.18.1.1/30 vrrp-group 10 accept-data

For security-conscious, You can add VRRP authentication and block VRRP packets from going out by using output filter.

After that, address 198.18.1.1 shall answer ARP requests with VMAC. Don't forget to clear ARP on Cisco routers.

HTH

Thanks

Alex

Hi Alex,

thank you for your reply ,

the first option is not available so I have used the second one. it worked as expected but after 20 minutes the VRRP mac address is overwritten by the duplicated MAC address. If I clear ARP on Cisco router I will get VRRP MAC back from Juniper and again after 20 minutes this MAC will be replaced. I have configured "arp-resp unrestricted" and "arp-resp unrestricted" on EX4300 but it is still the same. Do you know why is it behaving this way?

jiri

Hello,

20min is the default JUNOS ARP timeout.

What I suspect is happening is that EX sends ARP requests for CSCO IP using physical MAC rather than VMAC.

Unfortunately, ARP RFC is written in the way that ARP opcode is checked AFTER inserting src MAC into the ARP table, i.e. ARP request and ARP response could both update the ARP table.

You will need to add static ARP mapping on EX side to prevent this from happening.

http://www.juniper.net/techpubs/en_US/junos14.2/topics/usage-guidelines/interfaces-configuring-static-arp-table-entries.html 

HTH

Thanks

Alex