Thanks for responding. Okay, so just accepting default routes from each of the ISP's and using AS Path prepend to influence inbound & local preference for outbound will do the job of using one ISP as primary & the other as a backup in case the primary fails. That makes it a lot easier. Out of curiosity, if just default routes work fine even with Multihoming, why would a small to medium size enterprise want to have the entire BGP routing table? Is it so they have more control over routes to their destination etc.?
Coming back to my second question, since I am accepting only default routes, wouldnt a L3 switch do the same job? We have a few 3560CX's (WS-C3560CX-8PC-S - 512M of DRAM) which are pretty new but arent being used. Surely they can handle the current bandwidths we plan on implementing 100M & 50M?
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We are planning on multihoming our Internet and I would need some help on deciding the best way to set it up & also what hardware to consider.
Currently have a 100M link for our Internet with one ISP. But due to issues over the last 7 months with this provider, we have decided to have a 50M redundant link with another ISP – in an active/standby setup. Note: we might wish to upgrade the b/w across these links in the next 6-12 months to going up to 200M or 500M.
Besides normal web usage, we use the internet for a number of things – Office365, remote access VPN, site-to-site VPN’s and also to receive certain feeds. Hence, it is critical that we have our public subnet (& ASN) be available across both providers. I understand that for multihoming, we require;
To have full route tables from both ISP’s – which leads to significant overhead for storing route tables, & also CPU for processing etc.
2. We have full route table from Primary ISP & default + local routes from secondary ISP, AS pre-pend and ISP to change local preference (which will serve as the backup) – which seems to be a better option.
I would like to get your thoughts on;
Which is a better solution – option 1 or option 2?
How much memory does the whole BGP internet routing table require? And does multihoming with 2 ISP’s require 2x that much memory? (Current stats from Hurricane Electric shows there are 687,913 IPv4 Prefixes Observed)
Hardware to use? Would it be better to use a L3 switch like a Cisco 3850 (4G DRAM) or a router like an ASR 1000 series (ASR 1001 – 4GB/8GB).
I understand that these ASR’s are built to handle such processing and
With 4-GB memory, it can handle up to 500,000 IPv4 or 500,000 IPv6 routes
With 8-GB or 16-GB memory up to 1,000,000 IPv4 or 1,000,000 IPv6 routes etc.
But wouldn’t the 4GB memory on a 3850 switch be able to handle similar number of routes with respect to its memory? How much of the 4GB is actually allocated to TCAM in the 3850’s? And CPU?
Thanks in advance.
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Hi All, We have a number of sites in connected via an MPLS network with SP1. We are trying to set up WAN redundancy and have point to point links via SP2 (which we might ultimately use as primary links down the line, based on performance of the links). For this discussion, I have considered 3 sites, HeadOffice, Branch1 & Branch2. [Please see attached diagram - PS: these are just dummy subnets I've included :) ] HeadOffice: Cisco 3850 Stack --> Cisco 3900 routers --> PE Has 2 links to MPLS cloud (Pri & Backup) which are managed by SP1, and are running BGP between CE & PE. Has 2 point to point links - to branch1 & branch2 Subnets : 10.1.1.0/24 & 192.168.120.0/24 Branch 1: 2 Cisco 3560CX connected via trunk (& running HSRP for some interfaces) --> Cisco 3900 router --> PE Has 1 link to MPLS cloud managed by SP1, and is running BGP between CE & PE. Has 2 point to point links - to HeadOffice & Branch2 Subnets : 10.1.2.0/24 & 192.168.122.0/24 Branch 2: Cisco 3560CX --> Cisco 3900 router --> PE Has 1 link to MPLS cloud managed by SP1, and is running BGP between CE & PE. Has 2 point to point links - to HeadOffice & Branch1 Subnets : 10.1.3.0/24 & 192.168.124.0/24 Currently the primary links will be MPLS and the back-up will be point to point (which as mentioned earlier, we may change later). This is the design we have for failover, but I'm not sure if it will work well. Use static routes for the MPLS network and track using IP SLA. Use BGP between Point to Point links as failover. HeadOffice - 3850 Stack config : ip sla1 icmp-echo 10.1.2.10 source-interface vlan 250 frequency 10 timeout 6000 ip sla schedule 1 start-time now life forever track 10 ip sla1 reachability ip route 10.1.2.0 255.255.255.0 10.1.1.10 track 10 ip route 192.168.122.0 255.255.255.0 10.1.1.10 track 10 router bgp 64550 bgp log-neighbor-changes timers bgp 10 30 redistribute connected redistribute static neighbor 172.23.254.2 remote-as 64560 Branch 1 - 3560CX config : ip sla 2 icmp-echo 10.1.1.10 source-interface vlan 250 frequency 10 timeout 6000 ip sla schedule 1 start-time now life forever track 20 ip sla1 reachability ip route 10.1.1.0 255.255.255.0 10.1.2.10 track 20 ip route 192.168.120.0 255.255.255.0 10.1.2.10 track 20 router bgp 64560 bgp log-neighbor-changes timers bgp 10 30 redistribute connected redistribute static neighbor 172.23.254.2 remote-as 64550 And similarly for routing between Branch 2 and other sites. Will this work? I am yet to test it out. Does anyone have better suggestions and any config examples which would work better than this? Thanks in advance.
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Hi, We have two WS-C3850-24T-E switches stacked together and running the IP Services Licence. We are planning on getting a WS-C3850-12XS-E as we need around 12 x 10gig ports to connect to our servers and the only network modules that can be supported with the WS-C3850-24T-E are the 4x1 GE or 2x10GE. I need to confirm if WS-C3850-12XS-E can be stacked with our current switch stack of WS-C3850-24T-E? Also, if anyone has a better solution which is cost effective, do let me know. Thanks.
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