I have mainly worked at small and medium sized operators and we did not use IRR at all apart from registering our own and customer blocks with the one upstream provider we had (Level3) which required it. We maintained our own databases of customer prefixes tied to other customer information strict prefix lists were generated from. I have rarely seen as path filtering used except with large customers where maintaining strict prefix lists wasn't manageable. Phil From: ML Sent: 1/16/2013 19:57 To: NANOG Subject: How are operators using IRR? How are operators using the data available in the various IRRs? Using an example: AS1 is your customer AS1 has AS2, AS3 and AS4 described as customers in an IRR Also assume AS2 has IRR data describing AS1000 and AS2000 as it's customers. Are operators building AS path regexes such as the following automatically from IRR and applying that to your BGP sessions? ---- AS1{1,} AS1{1,} AS2{1,} AS1{1,} AS3{1,} AS1{1,} AS2{1,} AS1000{1,} AS1{1,} AS2{1,} AS2000{1,} ---- I would imagine most operators that are building policy from IRR are building prefix lists to limit what they are accepting. Is this being paired with some AS path filtering? Are operators just traversing an AS-SET as far as it will go and building prefix lists to represent all intended prefixes to be heard on a session regardless of who originates them? Is the possibility of AS1000 hijacking AS2000 prefixes towards AS2 a problem you as the upstream to AS1 need to consider? (Last question assumes AS2 made a mistake and wasn't filtering properly on it's own customers and AS1 is just accepting all prefixes under the cone of AS2) Thanks